Big point to keep in mind is the old sayin bout the harder it is to sand an prep the more important it is to do it right..as THAT is where the paint will lift an peel, it goes double for jambs interior an underhood areas! as it is obviously a pita to do, plus the grease, mildew an funk accumalted after years an miles, an sometimes its simply looked as not as important as the outside, but these areas area what helps show the level of work an detai lput into the job, ive had to do many over the yrs that i didnt have time or help in doin jambs an underhood, and even with an awesome paint job, these areas ruin the whole "finished" look of the car if not done right!
on a side note, dependin on the quality of paint your goin for, some bc/cc systmes( standox for one) wil allow mixin a hardener in the basecoat for a semiglos look, if yr not goin for a full custom glosy look,