Also might suggest in this situation - taking "before" pictures is fine, and helps with any "after" claim, but you REALLY don't
WANT an "after" problem!
Treat it like a rental company treats you. Voice your concern over damage, then do a walkaround BEFORE, and have them sign off
on the work order that there are no blemishes (or mark where any exist) - 'Cause you not only have to "inform" and show them there is no damage beforehand,
they have to agree with you and sign. Otherwise, they can always deny it and you are still stuck with a "he said, she said" scenario. This way they
KNOW they will be hit for sloppy work and will (hopefully) act accordingly. If not, then you have the documentation,
signed by them, to win your claim, with the added advantage of not needing a camera or pictures, so if you had not planned ahead you still have a way to protect yourself.
Also, if they are "covered with goo" or whatever (which in many cases is intentional) - before accepting and paying, insist on them being cleaned for a final walkaround inspection and
your signoff on no damage. You can always tell them your insurance requires it. That way if there IS a problem you can address it on the spot or even refuse to pay or remove the vehicle until speaking with a supervisor. (Like them saying it is the end of the day, no managers around, just pay and come back ...) You might save yourself a couple months of hassle.
Prevention is better than compensation!