Crayons are for toddlers.
Lacquer-Stix are almost as messy as crayons, too.
Nothing will give you a sharper, cleaner, more professional appearance than using paint. The Mega upper and lower took me all of 5-10 minutes tops using Testor's model paint, including clean up...
You thin the paint a little, get a big drop on the end of a skinny stick like a toothpick or similar, and touch the drop to the rollmarks. The paint runs in to the cracks like water down a gutter. After letting the paint air dry for about 3-4 minutes, gently wipe the receiver surface in a circular motion with CLP or whatever gun cleaner you have available and remove any excess paint. There shouldn't be much. I used shotgun patches to wipe the receiver, because they are thin and did not pull paint out of the rollmarks. Easy!
Hell, even the thin and shallow Bushy rollmarks on my beater turned out nice. This lower took me like 4 minutes to do...