I can sympathize with the frustration. We all use forums like these because we love talking about grappling (well, most anyways), so if any additional utility is found in the conversation, that's all to the good.
The main thing when it comes to finishing leg attacks in general, and heel hooks in particular, is that before anything else, you need to stick them in place. The more they can roll around or stand up or scoot away, the better chances they have of defending or escaping or reversing.
Eg:
Someone who is good at legs (or has put time into the situations in preparation for a fight) can do these things to take advantage of someone trying to play the same game (or go there on purpose to advance position).
That is one reason why the 'pull the heel across your chest' notion is wrong, because it's basically helping the opponent roll. When it comes to making submissions happen, you need to be latched on to them, need to knock them and keep them down on their hip, and to stop them from rolling or scooting. An opponent unable to stop you in one or more of these factors when attacking your own legs makes it possible for you to counter them.
This is also something that lends itself easily to situational drills, without even needing to go for full finishes; training partners can take turns holding leg entanglements on each other - like saddle, 50/50, or slx - timing how long they can maintain entanglements (i'd say transitions between positive entanglements without losing contact also count) vs how long it takes for their counterpart to escape or reverse it. To make more of a game out of it you could have it like half minute or one minute 'rounds', where the entangler maintaining position for full time gets a 'point', whereas the entanglee escaping or reversing before time gets a 'point', and tally up scores after X rounds. Likewise with more freeform rolling, catch-and-release is a fine principle for developing one's capacity to create and prevent the possibility of these submissions on a fundamental level.
If you can keep the opponent under control in your entanglements - keeping him from standing, keeping him from squirming about - then you have very little to fear from him in terms of strikes as well. (This can be another situation drill: within an allotted time, starting from an entanglement on a standing counterpart, see who can get the most time with their counterparts knocked down on their hips.)
When it comes to breaking mechanics specifically, there are a number of pressure vectors that can be in play, but in general the biggest one that a heel hook grip provides is the ability to use your large body muscles to impart rotational torque through the whole leg. In order to do this in a way that produces finishes however, it needs to be by means that twist the leg, without turning his whole body at the same time. Id est, you need to be able to move the leg in isolation from his body. This is another reason why the 'pull the heel across your chest' motion does not produce finishes; because while you may be imparting force on his leg, you are imparting force on the rest of his body too at the same time, and there is no 'backstop' for the motion; so the net torque that is actually imparted on the leg is basically zero if he rolls with it.
As a general rule, you will not move your arms themselves much when applying a break with a heel hook grip, but keep them tight to your armpit holding the foot, while using your whole body to apply the breaking motion. Inside heel hooks are one of the easiest ways to impart this rotation on a isolated leg without turning you or the opponent at the same time, as once you have the heel hooked and his foot behind your armpit, all you need to do is extend, and his leg will naturally straiten out into a position that is turned 180 degrees or beyond from where it should be.
Im a big believer personally in using the 50/50 and saddle as attacking positions (especially with a crossed leg Craig Jones/Lachlan Giles style). Outside heel hooks are somewhat more involved to get finishes with, not just in terms of isolated breaking mechanics, but also with respect to broader positional implications of the sort of entanglements where you might attack OHH's to begin with (such matters are interrelated of course).
50/0, or 'DOA', can allow for strong breaks, using similar mechanics as an inside heel hook, but the position itself is very weak structurally, a man attacking with it essentially putting himself into a hip lock or leg drag, where with familiarity in the situation, you have strong opportunities to attack with passes, back takes, head-and-arm chokes, or simply rain down strikes.
One legged X, or 'anaconda gwarch', is a much stronger position structurally, which a bottom man can use to stand up, or reverse the opponent, or transition to other leg entanglements. Attacking the leg directly from this is a bit more difficult however. The most reliable means is to apply a
leg knot or slide lock first; you want double leg control, to prevent the opponent from standing up, or rolling or scooting easily; and by freeing up the arms, you can apply a submission with full force on an isolated leg (this can be another situational drill: starting from a more 'neutral' entanglement, like SLX or 50/50, and working to advance to a more dominant chancery, such as a saddle or leg knot). Every other means of finishing with outside heel hook grips from SLX basically depend on achieving the same things a leg knot gives you first; an opponent stuck on the ground and prevented from rolling. One or both legs hooked in the inseam behind his far leg, stopping his roll, and giving you a solid base to move your body on his leg, almost like you're driving a screw, using your lat on the long end of his foot to apply rotational torque through the leg without rolling, like a toehold.
Studying film of yourself in practice and high level competitors in action is very valuable, to see what exactly is happening when they succeed by using a given move (like heel hooks); what is also important, is to see what is happening when you or they
don't succeed at using that move, to see what is different between the two; and thereby figure out the essentials.
May Just Bleed God bless you with many a dismembered knee to offer in sacrifice bro.
