I had a very nasty cut on the back of my calf, 12 stitches spaced out. Did not heal well. Ended up at hospital wound care center where I got excellent care. They used xeroform guaze pads. There are stretchy ace bandage type wraps that could work for arms, no adhesive. They wrapped my leg with rolled guaze.
I started out with one ER Dr who said there are 2 thoughts on healing. One is to let the wound air out for some time during the day. I tried that. Parts of the cut turned black. Wound care Dr cleaned it out and applied the xeroform pads which have a Vaseline compound to keep it moist. If you don't keep it moist, the skin cells will die. Keeping it moist is what worked for me.
After bathing I use a quality moisture lotion on my arms and legs. I think it helps. I get those purple spots at times but think the right lotion could help