Re: Mustang Washing
If you have a driveway and a hose that you can connect hot water too, that's all you need. Of course, the driveway will be an ice rink afterward unless you wait for a mild day.
I suggest going to a coin-wash where you can do it yourself. Brush drive-thru washes are OK and won't harm paint as badly as people think they would. I ran two over a seven year period and never had one complaint except from an old Mercedes Owner who lost some more exterior trim and asked if I had found anything (lol). Turned out he didn't lose it in my wash bay, but just make sure there are no loose items on the car and it'll be fine. A lot of car washes have a brush option, you have to tell the attendant that you want the brushes and he/she will activate them just for your wash; they're not necessarily used for every vehicle.
If the salt is bad enough, your best bet is to get the Stang undercoated every fall. A lot of places say twice a year is proper (once in spring one in fall), but even with 6-7 months of winter here, one undercoat will actually last two years with 20K of driving per year.
A brushless wash won't necessarily clean the paint, you'll be paying $8 or so for a wash that will leave a film over your paint. Only paint contacted items (such as brushes) will remove that film. A good car wash owner cleans the brushes before the start of each day, and sometimes throughout the day depending on brush use. If you walk up and notice a lot of black/green on a blue velvet based brush as you mentioned, I'd stay away. A little bit of discolouration is OK, but excessive black colour and other marks would turn me off right away. Hardened oil residue can cause damage to clearcoats.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!