Question on sound deadening spray

[Builderguy]

I need to spray some sound deadening material on the inside of the trunk on a 73 RR to match repaired areas to the existing material or just re-shoot the whole area. My question is one of adherence to epoxy. Normally would just scuff up the metal and spray but this already has deadener on it that has been sprayed with epoxy. I can't sand that worth anything that will help with the bite. Will the deadener (or chip guard, or undercoating, or actual deadener) stick to the unsanded epoxy? IDK as I have not done this before but I don't want to do it twice. The back of the two products only instructs one to use a wax and grease remover so maybe I am overthinking this. It will be painted after application has cured. The original material is hard as a rock. Thoughts???

 

[T2R9]

How long has the epoxy been on there? There usually is a window where you can topcoat it without scuffing. If its outside of that window a red scotch-brite should be sufficient.

 

[tnfastback]

I used Resto Ricks and it looks pretty close to the factory. As far as adhesion the undercoating would stick to anything as long it was grease or oil free.