i clean my RSST and Protank2 once every 3-4 tanks of liquid.
just run under water, rinse out the tank, soak for a few minutes, rinse again and then dry with a clean towel. then i do a dry-burn.
havent had to recoil my RSST since i built it up. the steel mesh looks clean. after dry-burning, the residue either burns off as well, or some whitish ash that i brush off lightly. using #500 mesh with 32AWG. i adjust my coils a little with a thin tip screwdriver to get even glow. after cleaning, the mesh and coil look pretty good.. havent found a reason to recoil yet.
for the Protank 2, same method as above. but i prefer to recoil silica wick once a week. find that it gets gunked up a lot faster than the rba.
i use a cheapo pen torch flame to prep my silica wick/kanthal/steel mesh. i burn the silica until it glows. i find this works a whole lot better than boiling. cos after boiling for like 15 minutes or so, i still get the silica wick taste. if i use a torch flame, the Protank is good to go with some fresh liquid.
if there is leftover
juice in the tank, i syringe it out first. i "test" the leftover fluid by dropping a few drops on the cleaned coils; if the taste is lacking then i dump it (but of course, the lacking taste could be due to some leftover water in the wick..).