3M and wurth make a gun that comes with a 4-5ft long flex wand that sprays in 180 and 360 degrees. You can get different cans of paint like rust fighter I, undercoating etc. Can get empty cans and put in your own paint like epoxy.
Sata at one time made a flex wand gun but dont know if they still make one, am sure its high dollar. The 3M gun can be had for around 60 bucks...Eric