Latex gloves are often used as a protection for both parties. The hand and arm are generously lubricated with a good water or oil based lubricant and additional lubrication is applied to the fistee's anus. The fistor next inserts one, then two fingers and when the partner's anal muscles seem relaxed, the hand is pushed in fingers first with the tips together in a closed ring fashion. Next the hand is slowly worked up inside. There are several sphincters or valves that block progression and these are opened by massaging or stretching the entrance area then pushing one or two fingers through and pulliing some of the intestinal wall back through.
Pain can be an indication of improper or dangerous manipulation.
The fist is slowly removed from the anus to prevent the hand from creating a vacuum effect and pulling a section of the intestine out with it. Fisting can lead to serious injury and is NOT considered safe sex practice. The anal wall is very thin and if torn can require surgery and the need to wear a colostomy bag.