6']['9- try multiple layers of SG. Since I started using it for this, I can keep the accessible areas on the backs clean with just carwash shampoo,. When I do pull them off, even the previously *inaccessible* areas clean up quite easily. BF and UPP seem to work well for this too, but I've only tried those on the pampered S8 so I dunno about a daily driver.
evil_c5- If you don't want to have them redone, and you don't want to try TOGWT's excellent suggestion (i.e., if the blistered areas don't really show much), you can try what I've done in similar cases:
Use a polish (I use 3M PI-III RC then MG) to clean and smooth the blistered areas a little. *Maybe* try some very fine wetsanding, but I never bothered and I'd rather have the extra paint/clear on there. Then just use the Klasse twins with many layers of SG. It's surprising how well this arrests the damage. I have damaged areas that've done OK with this method for many years.