I don't have much in the way of tools. A saw, 2 knives, drill, file that’s about it.
If I change a rifle I always start with the left hand thumb and cut this away from the rifle. I then cut the rifle off the figures left hand.
I then drill down through the rifle as far as I can. This makes it easier to cut out. Then I cut out the rest of the rifle from between the hands.
Thr hats I just cut a notch in the side of the one to be cut off with a knife. This gives me a start for the saw.
Then I just cut through, file off any ruff edges and glue on a British helmet.