I bought SprayMax (2K in an aerosol can) here in Canada at Nappa, an auto parts and paint supply franchise. Perhaps you have same shop or another that would have or a similar product. Spray Max is a German product.

I had EvapoRusted and touched up frame before clear coating. I actually ruined the down tube decal with the EvapoRust and had to replace. I don't think original decals had much clear coat. No problem with Spray Max over the original seat tube decal or new replacement decals I bought. It is suggested that 1st coat of clear coat be very light over decals and to let dry before preceding with further coats.

Re Prep: If not doing any touch up probably should clean frame well and degrease. I can't remember if I did, but for better adhesion and if you are feeling obsessive might be wise to rub down frame very lightly with some 1000 or 2000 grit wet sandpaper.