Forgive me, I have no doubt this subject has been done to death but I'm struggling to find an answer.
I've managed to get hold of one of these which seems to be the preferred weapon of choice for the job...
I've found loads of stuff on this forum and t'internet about actually doing the job, frequency, remote kits etc. but I'll be blowed if I can find anything that tells me what sort of grease to fill the gun with

Recommendations gratefully received. And sorry for the dumb question
