Don't think the plastidip would withstand much pressure washing. Done the grills on my old e86 & use to give it a fresh coat every month or so,used to try & Keep the pressure washer away from them.
could be a causative factor in mirrors loosening. When I replaced mine, i also edged them using sugruu to stop water ingress - rubber compound that sets but stays flexible. Has the added benefit of adding a nice thin black edge, so looks better