Still trying to throw fresh ideas out there.
If you plan on exposing the aluminum then painting then coating another color I think a masking is still possible. I’ll do my best to explain, i kinda wish I had a resin print to test and show with pictures.
>Powder coat raw aluminum gloss black
>dip handle pieces in masking medium(I’m personally thinking of something closer to a wax rather than something like latex masking because next step might pull up mask to easily, then again it might not, I wish I could test it myself.)
>take gloss black mask dipped pieces and polish raised edges revealing bare aluminum and leaving mask in recessed areas.
>coat bare parts with whichever preferred texture paint, let set and remove mask by pealing or with heat, if it’s more like a wax.