Ugh - and I thought my pressure sores were bad but that is truly grim.
Rightly or wrongly, due to the general 'you're young and capable of cleaning this and putting stuff on it yourself, unlike the majority of our patients'... I have done a fair bit of self care for icky ulcers/sores/wounds.
My go to is honey (which I have to be careful with as I am diabetic), and getting off it/elevating it - and that latter is frankly the most important part, and the hardest part.
There is precisely fuck all you can do lying on your front with your rear in the air, particularly if as a result you then have to spend the rest of your time on your back with your legs in the air (lymphedema).
This gets very boring and so most patients not in a hospital will ignore pain in order to stand/sit up, do something other than stare at the ceiling/pillow.
With a leg wound like that I cannot overstate the importance of him getting it elevated and keeping it elevated, regardless of how fucking boring it is. I can't heal some of mine at all really, because it is impossible for me to do this long enough for it to be of use (heart failure means legs in the air higher than my heart results in not breathing well, heart struggling further!).
The other things I have found useful - the clingfilmy adhesive dressings sold for tattoo after care, and a sterile gel that keeps things moist and flexible not dried out and cracked, which I buy from a veterinary site (comes in small tubes that way at a much lower price!). You must of course ensure no part of the dressing is on damaged tissue, ever, just use it to hold on a non-stick dressing or hold on gel/honey etc.