Well, I finally did it! Painted the calipers yesterday using G2 Mustang Vista Blue paint: this is a nice metallic flake blue paint.
I'm pretty happy with the result but if I were to do it again, I'd spray it on rather than brush. The paint is self leveling, but metallic paints tend to show the direction of brush strokes more than a solid color would. I think it still turned out nicely.
In the end, I decided to go with stick on vinyl letters instead of spray painting a mask (I made the stencil but decided it was too much of a pain to cover the car from overspray etc since I hand painted the calipers). If I decide to redo the finish using the same blue but sprayed on, I'll then take the time to use the stencils.
I used Oracal vinyl 951 which is a higher rated vinyl than used by the ebay sellers (the one linked here uses Oracal 751), so I hope it'll hold up well.
It turned out I hastily put the rear lettering a little crooked, so I picked it back off, marring the still soft paint in the process. It's not visible since I cut a new set of decals and covered the blemish but if the streaks bug me in the future, it'll be another excuse to mask off and spray paint the whole thing again.
One tip: I suggest sanding off the factory Tesla text so it doesn't potentially show through the caliper paint, but this may vary depending on your color choice. I was also pleasantly surprised to see how clean the Tesla calipers are regarding brake dust: regen braking really minimizes this!
I obsessed over the lettering and wanted a perfect factory match. As you can see below, it came out pretty well. After laying out the TESLA text, I actually see that the Tesla factory lettering has the "L" moved over to the right by about the width of the upright. I decided perfect spacing of the 5 letters looked better, so I left it as pictured. Anal, I know. If you look at the cardboard proof I made, the factory lettering fills the cutouts close to perfectly, with the exception of how the L is kerned.
In case anyone wants to do the same, the front text measures 7mm tall x 99 mm wide, and the rears measure 6mm x 80mm. I'm willing to share the Silhouette Studio v3 cut file if anyone wants it. I don't know how to export it to a generic cut file.