Some more feedback on this topic.
I just re-gripped an eps/epoxy board. The grip was in 4 different sections. As per the pic below the section that has the most leftover I just used a plastic scraper. The other 3 sections I used a hot air gun. This was set at 200deg.C and using a scrap bit of grip I tested how long the heat dissipated through the grip before using it on the board, this was about 5secs, enougth to soften glue. Any longer and it will melt the eps core and delam the board.
The method was to run the gun across and peel at the same time.
As you can see in the pic the hot air gun is the go. The first section took 30mins, the other 3 took 10mins each and the glue was cleaned off with tea tree oil.