Why not just topcoat the DP with the 2K then store them?
I would be willing to bet that scuffing the DP just prior to the 2K, in the future, would be fine, just as your paint shop said.
PPG does have a good tech line--I think the number is on the Tech (p) sheets? if not its on the net, Ask them. I got soem realy good advice from them regarding all the different hardeners that can be used with DCC Concept.