Best trick for salt stains (DIY style) is a slight variation of what Dubweiser said.
In this order:
1) Shop vac to remove as many chunks as possible. Breaking off larger peices and dust makes the next steps easier
2) Use HOT water, not warm, in a spray bottle to dissolve the salt/calcium stains. Scrub with small plastic brush (bathroom type)
3) Use a Shop vac to suck up the water as you go. (repeat steps 2 and 3 as many times as needed to eliminate the stains)
4) Spray Zeps Carpet Cleaner (or vinegar if you want to save $10) on freshly cleaned area. This will neutralize the alkaline solution created by diluting the salt/calcium and avoid damage to the carpet fiber.
5) Final shop vac to remove as much liquid/moisture as possible.
6) Air dry in ventilated garage, or leave the doors open in the sun for a few hours.
BTW, Dub, the car looks good. Nice job. *tu*
