SO WHY wouldn`t a tar remover like MK37 Tar and Adhesive Remover work on this "rust-proofing"?
And if it`s on interior cloth or carpet fabric, here`s what ValuGard (Tim`s Tech Tips) says to do:
"First don’t panic and grab a towel and start “rubbing” the spot. This will onlysmear the product and make it worse.The best product in your arsenal to remove under coating from cloth is the VG103 ValuGard Fabric Protector.The solvents that are used in this product are of course safe to use on interiorsand make an excellent spot remover for under coat, grease and other petroleumbased stains.
First spray or pour a small amount of the fabric protector directly on the spotand allow it to start to break down the under coating, then using a clean terrycloth towel gently “dab” at the spot without rubbing. Continue to spray and dabthe spot using a clean part of the towel until it is removed. Depending on theamount of under coating this may take awhile. It can also be used on the hardsurfaces."
AND, for ValuGard`s own VG-076 Hybrid Rustproofing, this is their directions for clean-up:
CARE AND CLEAN UP OF EQUIPMENT
Spray guns, brushes and tools used for application, should be immersed in soapy water or mineral spirits when not in use. Driedmaterial can be removed with mineral spirits.
(Which is what Ron Ketcham suggested in the first place)