Have your tried a Paint Marker? That what I used and its looks nicer then a Sharpie and doesn't comes off as easy.
Mugen MBX6T - Ninja JX.21 with EB Mods Headbutton, O.S. 2060 Pipe, DX3R, Hitec 7955TG Servos on LiPo
HPI Cup Racer - Murfdogg Synergy 17.5, Tekin RS Pro, 2S 40C 4200mah, DX3R, Sav÷x SC-1251MG Servo