The first part of my working life was spent in the printing industry, thankfully only about 10 years of it, we used to use a noxious substance named MEK (Methyl Ethyl Ketone) later found to be highly carcinogenic. It was used to swell small dents in the rubber transfer blanket to bring them back to the correct surface height, but it was only normally a temporary fix to finish a print run, eventually the transfer blanket would need to be replaced.
With regard to fitting footrest rubbers, you only ever have to do this once in the life of the footrest rubber, when they are worn out you can simply either twist and pull them off, or if that proves too difficult, slit them off with a sharp blade, I don’t think I have had a footrest rubber last 30 years in use, I was politely told by one of my “Old Boy” MOT testers, RIP. that he could fail my bike if the footrest rubbers were significantly worn out as your foot could slip off them!
Mine currently need replacing as the HRD lettering has completely worn away (both sides) they were fitted new for the International in Italy, so have not done too bad, better get the kettle on without any more ado!