just some coins to watch for:
silver dimes, quarters, halves; (dunno if your car wash/es handle many cents, but...) wheat cents;
Indian Head cents; the newer W quarters; proofs; buffalo &
V nickels;
War Nickels; foreign coins...
there are too many different errors & varieties to list, but there are mintmark errors & varieties, lamination errors, clipped planchets, rotated dies, mule coins...
there's a lot to be watching out for. dunno how much time you get to sift thru everything, but if it were me i'd be making time to sit & sift. if I couldn't do it all myself i'd get a helper. once you start sifting & searching with some regularity- combined with the knowledge you'll no doubt accumulate along the way- you'll sort of develop your own search criteria & methods. with the mass of coin accumulated even from just one car wash i'd think your chances of finding interesting & collectible coins are quite high. i'd come out of retirement to do that job. I love searching thru huge accumulations of change, one of my favorite things to do.
color me slightly jealous, lol!