Early rust on trailer hitch

Yes if you have brand now "clean metal" there is Oil in the pores of the Metal so the Etching as a separate step is best and yes it cost more to do it however the cost is one time and you will not have to worry about it after that. The Main thing with the Paint to keep in Mind is that it is a 1 coat deal Not like spray paint where you do several build up coats.

Get the best paint brush you can find and that is not the cheap plastic Bristol ones don't worry about "Brush lines" the paint is self leveling just do a Nice consistent medium thick coat without back brushing over it let it set. Below is a 1931 Caddy Frame done with it.