I need to reinstall a car badge. It's of the lettering type so I can't use a big fat pad.

Has anyone got good experience with 1 cleaning down the back of an old badge and 2 how to reapply a suitable product (happy to cut to fit if needed) to stick the thing back on.

I would use a good quality double sided tape that would require trimming to the shape of the letters with a craft knife (scalpel type).

For cleaning the back, a "sticky label" remover that can be purchased in a supermarket or hardware store as it should not damage the back of the (plastic) badge and can be easily washed off.

Perhaps talk to panel shop and enquire what type of tape they use to reattach badges. They might even sell you a strip to do the job.