How do you do it?

FOR Lowers :
Weld a washer on the flange lip and press out from the back.
Heat up the rubber till it comes out and use a panel cutter down two sides of the sleeve.
With rubber removed VERY CAREFULLY use a torch at a shallow angle to cut the sides of the sleeve.
For uppers:
BFH and a vice or section of tubing or pipe
Vice and large socket
Large sockets and all thread