I'd be concerned that the shop vac is blowing high velocity debris at my paint.
That’s actually not much of an issue since the air that comes out of the outlet goes through the vacuums filter 1st.
@OP. What kind of attachment are you currently using? Is it something that looks like this blower wand? If so, that’s about as good as it’s going to get when it comes to what’s available for the typical wet/dry vac.
I hook that up to my 6.5HP Ridgid to sweep the backyard patio and it does a great job at that, but I wouldn’t consider it quite good enough to go drying cars with because IMO it just doesn’t put out enough air to get that job done.
If you were to compare it to a corded Toro leaf blower for example, the leaf blower walks all over it when it comes to air & force it’s able to put out and the leaf blower can be had fairly cheap for around $100
At the end of the day I wouldn’t consider either of them to be particularly safe due to having to wield such a long attachment near the vehicle and eventually an accident is bound to happen unless you’re the type who enjoys staying tedious 100% of the time.
If it were me I’d just invest $25 and get the largest version of the Notorious Dry Towel from Speed Master and only use air to dry the wheels & tires, grill, emblems, etc.
A good drying towel is faster than drying with air and doesn’t scratch at all. You don’t even need a “drying aid” either.. Nobody needs an aid, you just need a good quality drying towel.
