Quality cresting really needs to be done with a cresting machine, either store bought or home made. if you are meticulous you could try building a cradle like rod builders do. you could even build a cradle out of 2 pieces of wood with a notch and a piece of felt to pad the arrow.
If you wanted to do a simple cap dip you could spray paint the cap with paint bought from the DIY store. i just tape off my cap at 10 inches with blue painters tape and do 2 or 3 light sprays on the shaft, if you mess up, use a paint thinner to remove as much as possible, sand and try again.
As for a home made cresting machine, do a search and you will find several threads. i have included a pic of the one i made, its not perfect but it works, although i need to improve it some. it is made with a used sewing machine motor i bought for 10 dollar at a sewing machine repair shop, some scrap wood, a dimmer switch and a scrap extension cord.
Good luck and let us know how you do. Jack