Old Carbon Booms are usually difficult to strip because they used to use good quality glue.
The modern ones are easy as they only use Clag which is water based

When I grip my own personal booms I always use plain black & put the join to the outside although our production booms had the join at the bottom with few problems.
The hardness & colour of the grip also has a bearing on adhesion for some reason.
I used to always encourage people to have a go at it first, that way they they were happpy handing over the money when I did it for them

By the way we don't do regrips any more but can recommend Steve Strat as he does a good job.