Looking pretty good bro... that's a big beast!  I usually go for hand painting over masking myself, but here's a tip for painting light colors over dark ones... get yourself a can of Rustolem Clear Satin (in a rattle can).  Spray it over the dark paint you want to paint over.  Then paint your light color.  Sometimes I've found that the dark color will bleed into the paint if painted directly over the top.  One thing too... allow the paint to dry and cure completely... usually overnight... to prevent the color bleed.  That helps alot!  Keep up the good work thou!