Casting on with two colors HELP! ASAP - TIA!

For the knitting olympics I am doing a colorwork hat with 6 colors. The cast on uses two colors, casting on 2 sts with each alternately for a total of 120 sts. I have been knitting for 20 years but have always shied away from colorwork, never using more than two at a time and have never used two colors to cast on before. Is there a special technique for it? Do I need to twist the colors together to prevent holes? How do I carry the yarn to hide it? Help! I feel like such a newbie…LOL. Any tips will be greatly appreciated! Oh, and the sooner the better since I’m supposed to be casting on in 7 hours :shock: . I really should have decided to do this earlier shouldn’t I!!! :doh: I hope I don’t end up with a tangled mess of 6 colors instead of a hat!
TIA!