Today's multi component finishes cure pretty rapidly once applied. You need to make sure that this is what was applied (chances are it was). They cure thru a chemical reaction between the two components, much like body putty does. The hardener causes a cross-linking of the molecules when mixed with the resin (color portion). The majority of the solvent evaporation occurs within a couple of weeks, and in todays coating, the solvent content is actually less which helps. I have used Dupont Chromabase for many years and it will get hard enough for you to wax and put on a bra within 30 days. I have a bra on my Harwood hood which is Chromabase and it looks like it did the day after I painted it several years ago. My car doesn't get wet though. I would say with a non-baked, non-factory coating, I would be hesitant to allow a wet bra to rest against the paint, so if it rains on your trip, take it off (provided it had enough time to cure in the first place). In my humble opinion, the shop is telling you 60 days to prevent any warranty issues.