I've never seen all of the match in question, but wasn't HBK's selling considered to be laughably bad and totally business exposing? I've seen parts and he makes Hogan look like an idiot with his cartoonish oversells.
Correct. Shawn was doing backflips off punches and flopping like a fish on dry land. A good sell job is one where they don't overdo it and still convince the crowd and viewer of the legitimaticy of the injury. Some people like Savage or Hart would sell a knee for a month, even if it was a squash match.