@njlarry,
I had my O'day 25 media blasted and
@Scott T-Bird had his blasted by same yard. Both ended up bare gel coat. I'm not sure if a barrier coat was on either boat and taken off by the blasting.
As far as hot coating barrier coats, Interlux InterProtect 2000E can be over coated up to 6 months per Maine Sail. I just used some on a keel cleanup and the only mention to hot coating was after the last coat of IP2000E to put on bottom paint while the barrier coat was "thumb print" soft. I did find instructions for IP2000E a little intimidating but I think I would tackle it.
I checked my notes and only spot painted last year. This spring some of the black bottom paint put on 3 seasons ago was showing through the blue I've been using so I believe the Hydrocoat is sloughing off or coming off during power washing.
The Seahawk Monterey tech sheet says it is a harder ablative for fast moving boats. I'm sure a softer ablative will build up less on our slow boats.
I like the lower cost of the Neptune HRT. Noticed it has 25% copper compared to Hydrocoat being 40%. Interested in learning if it is softer and ablades faster for less build up. Looking forward to your fall report.