Dark Knuckles From Punching Bags; What Percent TCA Peel Do you Recommend?

I have brown skin.I prepare the area with 3% hydroquinone every morning, and a mixture of retin-a .05%, hydroquinone 3% and hydrocortisone 1% at night with little lightening. I plan to do a tca peel after a month of the above is finished, and was told to use the 20 % because anything stronger takes longer for the skin to flake off. My skin is very resistant to peeling(does not peel with retin-a combo or mild peels.) Please help, im lost where to start.