Be very careful with heat. If you use heat from flame it can set the pen on fire easily ( I´ve done that on a Vacumatic) and if you use to much heat from a heat gun or hairdryer the celluloid can expand/contract. If you never don it, try it first in a pen you don't mind to ruin.
Urk!
I've been pretty cautious with the heat tool, and so far I've used it on two Osmiroid 65s, a little third-tier pen, and the Sheaffer Balance. I'm not taking any of my pens anywhere near an open flame! The heat tool I have is one used for rubber stampers to melt embossing powders and suchlike.
The nicer pens I'm happy to send out to experienced people for repair until I'm a lot more familiar with pen innards
Very good point. So many pens have been wrecked by amateurs as part of their learning process.