John,
You have several options.
Easiest...just get a fresh CE2.
The next easiest for me is to just get a really high PH all PG cinnamon
e-liquid (Atomic Cinnamon from Tasty Vapor with NO sweetners added is what I have), keep the
coils wet with it for a few days, do some burns without inhaling before refilling the carto, then just keep using the carto. If it has ash on it still, I just leave it on there, but if you like you can attempt scraping some off gently with a wooden toothpick. Rinse out the carto with distilled water or PGA, then fill it with whatever flavor from there. It may take
vaping through a fill to get all of the cinnamon flavor out, but it works for me.
Next:
You can pull out the seals and flush it really good with distilled water, everclear, or vodka.
If you like you can gently pull the wicks out, burn them off with a torch and push them back in.
I've also dropped them in the ultrasonic glasses cleaner before, it works OK, but it can also cause the wicks to fray a bit if overdone.
It is possible to get the sleeve off with the right tools.
If you have a dead battery laying around, screw the CE2 on that. You can also use a working battery, but be aware that this method can put stress on it, and possibly break the battery or mangle the threads.
Hold the battery firmly in your fist and push the carto with your thumb. Use a firm push, but not too firm.
Rotate the battery some and repeat, repeat, repeat.
It can take a while to loosen it up, but eventually it should wiggle off.
Touching the base of the carto with the flame of a butane torch can speed up the process a bit.
I've yet to see any with 'solder' in them...it's just 'crimped on' there, the heat just softens up the metal a little.
When you're ready to put it back together, run a bead of super glue around the base, or wrap it in teflon plumbers tape (trim the excess tape after it's back together).