Having no particular issues with mine, especially not the enclosed-wick ones which surprised me quite a bit. I haven't rebuilt the old-style coils yet, but I do make sure to clean them well regularly. If the coils are fairly new I just take 'em apart and rinse each part in the sink, but when more thorough cleaning is needed I do it like this:
I take the chimney and cap off and rinse each part well with lukewarm water, then I let the parts soak for a day in an alcohol solution. I take them out, rinse them with water again and finally dry burn the coils with
short pulses while simultaneously blowing on the coil until they are clean of residue and glow evenly.
And that's that. Put the chimney and the cap back on, pop them back in the tank and continue to chain-vape relentlessly.

Of course, the newer coils can't be taken apart that easily so I don't disassemble them and basically dry burn on feeling alone, making sure to not overdo it.
I do wonder if I can actually skip the alcohol bath and go straight to rinsing and dry burning.