You'll find it easier on mat fiber. Most RC surfaces don't have enough "tooth" to hold the oils, unless you spray them (Marshall's makes something called Pre-Color Spray). I hope you're also trying pencils. They're great for detail areas.
"This week's project has turned into Bromoil prints and I also have easylith and bleach on the way, lol. Nothing like taking it one thing at a time, huh?" Now you're sounding like me. I've been struggling with Bromoil for a few months. Close, but no cigar... Please post with your experience.