The rubbing alcohol I use or have is only 70% isopropyl. I assume the other part is just water. Can you get it at a higher percentage? I have not even looked in stores. Just used what I had in the cabinet. Seemed to do fairly well with the exception of one, where the coils still look dark. Wish I could find some type of soft bristle brush I could fit in there so I don't mess up the coils when I brush it off. I also have some white vinegar I thought I would try. If it takes coralline algae off a fish tank then it should also clean coils....
For my RBA coils I use a clean mascara brush. Wonder if you could bend one to fit into a Shifu...?
I've never used a brush of any sort on my coils, but would love to know your experiences. I have used a toothpick and gently scraped at the coils.