My mantra is, get outside the strike, secure the bastard (usually by getting counterpinning his wrist), turn away to lock him in and slam your outerforearm down on on his attacking arm to pin his elbow and force him DOWN. This is the message that O/J/K/CMAs are telling you constantly: when he grabs you, or throws a punch at you, he's making a limb vulnerable. Take him up on his kind offer, pin the bloody wrist, turn, project your weight into the strike to his elbow, and once he's forced down, you can deliver...
(i) an elbow strike to the face (`chamber to the down block') followed by a hammer fist to the throat (aka `down block')... and there you have the very first two moves of Kicho 1 and 2;
(ii) proceed from the elbow strike (`chamber to the outward block') to a hair or ear grab, then pulling the attacker's head down with his arm still trapped (`outward block')...
... and any damned thing you want to do further, most typically
(iii) stepping forward while he's still reeling and delivering a palm-heel strike to his jaw under his ear, if you're feeling charitable, or his larynx, if you're not, or something similar.
Muchimi plays a bit role in this and that's something else I work on. The smooth and automatic transition from striking limb to gripping limb is very effective but not automatic. I'm still getting the hang of it after four years.
The main thing I train is controlling the aggressive limb—whether it takes the form of a grap, a punch or whatever. If it's a grab, it's easy. If it's a punch, it's trickier, but if you've used a proper `Fence'-type defensive setup, deflection of the striking fist into a trap on that arm is largely a matter of practice. It lets you deflect to the outside, but if you can deflect to the inside, then you can get outside and then things are as in the first scenario. There are many variants, but basically, the attacking situation requires him to project one of his limbs close to you. My main SD practice consists of reflexive incapacitation, ideally by control, of that limb. Once I've got it, the SOB is anchored and locks, pins, and other controlling moves can be applied that will culminate in something very nasty happening to his larynx or carotid sinus, ideally, using the non-controlling hand.
When I'm inside, it's a little different. But not that much. Deflect with the Fence, turn and hard elbow to face, grip and low sidekick to the side of his knee with sincere intent to rupture his knee joint. And knifehand to the throat, again. There are many variants but there's a common thread there...
Not very elegant, I know, but Kwan-era TKD wasn't elegant at all... :EG: