'moanin everyone.
Jeesh, I post about the early bottom coil mini tanks and everyone talks about cartos. Cleaning them was a joke. The gunk that builds on a coil, any coil, is actually a polymer, yes a type of plastic. Denture tablets, hot water. PGA and any "industrial grade" solvent I've tried, like acetone and others, won't touch it. The only way to get rid of it is by dry burning. Dry burning a carto kills the carto so they are throw-aways.
In terms of cheap, not including the time, I don't think rebuilding with cellulose and a new coil costs more than a nickel, literally, including the wire. The advantage I've found with cellulose is how long it lasts compared to silica, and from what I hear from others, cotton, hemp and everything else. I put at least 75ml through two Protanks I rebuilt with cellulose and when I re-wicked them I actually could have gone on to at least 100ml. I do vape tobacco flavors with minimal sugars and that's a big advantage, but if I got 30ml out of a stock Protank head that was pretty good. The box of cellulose I have should produce at least 12,000 wicks and cost less than fifteen bucks so it's hard to get less expensive than that.
The thing that really strikes me about cellulose is that when the density is right, and that can be a little tricky until you get the feel for it, whatever you wick with it suddenly becomes a whole, new, vastly improved device. Single coil devices produce vapor and flavor like or better than dual coil devices. Imagine a CE3 that performs like an iClear 30 series on steroids. That what it's turned into for me anyway. That makes rebuilding well worth the effort.