Well here's one of the cookies I did with the sanding sugars applied right next to each other. Thanks to everyone's advice here I did it for the first time with these "Joseph" cookies and they turned out great.
A lot of people are asking how I did them so I thought I'd post it on here. I first did the outlining in black one day and let that sit overnight. The next morning I attacked the coloring. I would fill about 10 of the red sleeves with icing then go back to each one to apply the red sanding sugar, tap off the excess, then use a clean "blush brush" from any make-up department (mine is only used for cookies) to brush off the stray sugars that stick even after tapping it off. After doing the 60 cookies in red I went back to the first ones to do the orange icing/sugar and was pleasantly surprised to see that the red was dry enough that the next orange sugar didn't stick. No stray orange sugars stuck to the red sugars although there were a few orange crystals on the remaining unfrosted parts of the cookie so I brushed them off again and repeated this whole process with the rest of the colors. It took me 4 hours to do all 60.
So if you were only doing a few cookies that would translate into about 45min drying time for one color before moving onto the next. Much quicker than I expected.
All that sanding sugar over the entire cookie made it taste a little sweeter than normal but I LOVE a sweet tasting cookie so I didn't mind a bit.
It was my first time covering an entire cookie with all these sanding sugars. I charged my normal charge for them because the customer wasn't even expecting me to do that but it's Joseph's colorful coat...I just HAD to do it!! I would definitely charge more for this extra touch in the future!!
Thanks for the many nice compliments on these cookies!!!!!!