As far as tips go, I keep mine CLEAN and DRY, and keep them in plastic storage bags. I know guys who keep theirs in lacquer thinner because they don't have the patience (or professional hygiene?) to thoroughly clean their spray tips. Some guys don't care, as they're a write-off anyway...To each their own...
I have a "tip keep" in mind for this summer, just a chunk of foam with appropriate holes drilled to slide my clean tips into...
Dealing with customers? Well, you get used to it...A thick skin doesn't hurt...