A lot of great stuff covered but I'll add or repeat a couple.

1. It has been mentioned above but I'll reiterate that catching and countering from the same side , particularly against a hook is key to stopping momentum.
2. Don't go for all big shots, counter with speed, keep them short and when you have room, extend.
3. Change levels on your punches.
4. Work on some bread and butter, left hook-left upper. Left hook body, left hook head, right upper
5. Don't stop moving your head or your feet just because you are inside, change angles
6. Bump left, right, back, turn. There are lots of little footwork moves to improve your position.
7. When you slip, slip in to punching position.
8. Don't wing, keep your punches tight and your elbows in.
9. If you are an inside fighter you have to punch as long as you have a hand free. Don't let your opponent clinch without paying.

Two other fights that come to mind Corrales-Castillo and Ward-Augustus. Buddy McGirt was a master though.