I used to take my car to the coin-op car washes as well when I lived in a condo.
Like Lynxis said, don't use the brush.
Instead I would bring a bucket, a wash mitt, soap and a chamois.
1) Drop in some coins to pre-wash and fill the bucket (usually about $2)
2) Wash by bucket and mitt (use grit-guard if possible)
3) Drop in $2 to rinse
4) Then dry with chamois
Scratch free wash for about $4, but it also helps to have Opticoat.
I still do this sometimes when I'm too lazy to unravel the hose
