Would the "experts" on this newsgroup advise a newbie to use a sealant
gun for sealants/caulk/mastics.

Last night I was struggling to put on some sealant round my door and
window frames, using a squeezable tube of sealant. I nearly dislocated
my thumb from the constant pressure I needed to apply and if gravity
was against me, the job proved to be impossible.

Time to get a gun?

Bruce