Use white out or model airplane paint and Remoil on a rag will clean the excess up. You can pretty much smear it on the lower and the Remoil takes it right off and leaves it in the engravings.
The crayons work great. Heat the reciever up a bit with a hair dryer and press hard. Wipe off the excess, no mess. Mine has held up great the last 2 years.
I used a small Testors paint brush and Testors enamel paint to fill in the rollmark, let it dry completely, then lightly rubbed off any extra with paint thinner dabbed on a t-shirt and once more with CLP. Do dark colors such as red first or they will bleed into other sections such as white if you choose to do multiple colors. If you have any questions, you can PM me.
After reading this I just did mine this morning with red crayon,worked pretty neat. I got some crayon in the engraving where I didn't want it so I use a needle and rolled it right out. Only broke 1 crayon but I don't think they'll miss it.