How do I paint tire letters?

You could try drybrushing them if they're raised. Or you could use a white pencil crayon.

I don't know, I'm new here.

Good Luck!

Falcon,

I'm not a bit automotive modeler but I could swear that I once saw somewhere that you can get aftermarket decals specifically for tires.  You might want to explore that avenue.

Good luck, best wishes and welcome to the forum!

Eric

I do  a fair amount of car modeling .  I use a pencil  eraser.

give the eraser end a round shape  than dab it onto  a thin layer of paint.

the eraser will absorb just the right amount and get a little sticky 

than gently start dabbing over the lettering , you can increase or decrease the amount of white by

dabbing the eraser  on a sheet of paper.

I use acrylic paint so if I make a mistake a wet brush will flood it out of the crevices

 I finish with a seal of dullcote or satin clear

a lot of guys use the white gel pens , I haven't tried them yet

there are decals also , you have to spray gloss(or future) the tire first, apply the decal than  spray a flat or satin to blend them in

I just finished a Spitfire that had raised "DUNLOP" lettering on the tires.  I used the drybrushing technique and it turned out fine.