Double Processing simply means, picking up a design on your rubber stamper, then stamping another design over top. Simple explanation, but I wouldn't call it easy. For starters you need to work quickly, even quicker than regular stamping. For the initial design, you need to use a nail polish that doesn't dry too quickly, preferably a cream finish.
Using this method gives the ability to stamp a design onto another design, probably best to use a block pattern or symbol as your second design.
NYC "Lolly Pop", Sally Hansen "White On" and Ulta3 "Purple Pumps"
I began with the foiled pink shade of "Lolly Pop" as my base colour. Then using "Purple Pumps" on a stamp with an intricate design, I proceeded to press the stamp onto a giraffe print type stamp, any remaining design created with the purple polish just got stamped back onto the plate. Clear as mud? I'll show you the result..
If interested google search "Double process nail stamping" and you'll find helpful tutorials.
What do you think? Would you try double process nail stamping?