When you say "touch up" what are you referring to? Dings? Chips? Large areas? Polyester and the Urethanes referred to here are finishes that do not combine with any other. I'm not sure how to describe it really, but I'll compare it to nitro. When nitro is applied to nitro will 'melt' a little into the surface of the previous layer. Poly and Urethane do not. They will only 'bond' with the surface if it is rough sanded. This makes spot repairs a little more difficult as it will not blend really, and surface repairs ahve the potential to just fall off.
I use a production polyester on my guitars. However, I have plans to use the same urethane product Fender applies to their American Strats this year as a proof of concept. Neither product 'melts' any layers underneath when the next is applied. Both of these are a mixture of 3 components, plus a thining agent if desired.
If your plan is to recoat that PRS then you should sand it well, especially in the really hard to get to places, using a fairly course grit paper. This is especially important because you don't want the new finish to flake off if the body gets bumped down the road some time. In my shop we use 180 grit between layers. I don't know what other readers think, but the thought of using household coatings on a PRS sorta makes my hair stand on end. Are you sure you can't just fill the the bad spots and buff it out again?
For dings and such use System 3, T-88 or other high strength epoxy. DO NOT USE HARDWARE STORE EPOXY AS IT DOES NOT HARDEN - EVER!! That means stuff from Home Depot, or Lowes, or wherever.
I think this is information overload, but I hope you find it usefull just the same.
-Doug