I started using Monokote in 1985, was difficult then, still is. I think our airframes are much lighter today, this addes to the adhesion issues, you just can't pull and push like you use to. Case and point, turtle decks, use to be a big foam block with balsa skin, now-a-days same skin, much less foam interior. More use of lite ply on the exterior of models, sides were balsa, now lite ply. Monokote sucks right into the grain. I continue to use Monokote because the roll to roll match better than Ultra kote, I find the seams are more durable, I can buy 25' rolls, once shrunk it seems to stay. The paint doesn't match very good, I switched back to Monokote before Ultrakote offered matching paint so I can't speak to how the Ultrakote matches, the Monokote just plain sucks.
The planes that I covered with Ultrakote I was forever shrinking, ironing down loose fabric, sometimes taping together where the seams let go, and there was no matching paint.