Lot's of good stuff here. Cooling, mixing, venting & maybe a GOOD mask, not just the paper ones, the ones with the replacement filters.
A trap/drier/filter... two won't hurt, and I run at least one paper filter too and change them often.
You get lube suspended in the compressed air as well as moisture/condensation from pressure changes and airflow past restrictions in the lines etc. The longer a spray lasts, the cooler the areas around air expansion areas get and the more condensate collects there... I always use a paper filter as close to gun/brush as possible to trap any condensate happening between trap filters and brush.
