First Timer with SImple Mod Question

Ok so I bought the Wal-Mart Exclusive DotM repaint of Sidearm Sideswipe. He is an absolutely fatastic character...except for those blasted all-spark blue guns. Now say I wanted to take those abominations and turn them black...what is the best and most cost efficient way of doing so? As a newb I have only thought of the following two ways...
Spray Paint- Seems good but I'm worried about coverage and globs
RIT Dye- Dont eve know if it works but seems like the easiest way to guarantee complete coverage.
So what do you guys recommend?
Spray Paint- Seems good but I'm worried about coverage and globs
RIT Dye- Dont eve know if it works but seems like the easiest way to guarantee complete coverage.
So what do you guys recommend?