How does the stinking thing come off? Just screws as one piece
through the hole in the bottom tube?
Yep, unscrew it from the tube. If it's really dirty and stuck, spray with some penetrating oil.....let it set for a while and then unscrew it.
After you get the switch off, clean it really good with denatured alcohol....then:
Use a small amount of JB Quik and attach an old carto or atomizer to the button....let set for about 30 min. Take a flat head screw and do the same for the plunger
After about an hour it's set enough to hold.....so unscrew the top from the plunger
Since you don't give the JBQ time enough to fully cure, work back and forth and the two button pieces will detact from the tube and screw head. If the button is hard to remove from the tube, gently squeeze the tube with pliers to deform it and the button will drop off.
Peel off any JBQ residue with your fingernail or a plastic coffee stir stick
Once it's clean, reassemble and tighten everything up with your hands. Hand tight is good for GG parts.