Sorry it took me so long to get back to you. I had a little plastic measuring scoop that held about 3 oz. of hot water. To that I added a teaspoon of Cayenne. Let that bloom (or steep) for a couple minutes to release the capsasin. Then I soaked my finger for about ten minutes. Did this about three times a day. Capsasin will eat any infection (including skin cancer btw).
You're right. Cayenne water will mold quick, usually within a couple days. So I made fresh for each soak. Cayenne is cheap, 3lbs for about $15. More than enough to last.
Now I didn't read on how to do this or anything, I just did it from past experience. Used a cayenne and Epsom Salts soak prior to my finger incident to cure my foot of copperheadess bititis.
Oh yeah, I just remembered where I learned it. My farrier told me one time he cut the tip of his finger off. He didn't know what to do as he had gone to the doctor and his finger was in constant pain. The lady at his local health food store told him to stick his raw finger into a 35mm film canister full of dry cayenne. He did that off and on for about a month. The pain went away and his finger healed. Now I figured if it worked on his finger, it would work on mine. He had told me that about four months before my incident.