I used to get it on my neck really bad, Mach 3 Turbo with Nivea for men shave gel (the menthol one) and Nivea aftershave. Works wonders, if it doesn't just try different shaving creams/gels until you find a good one, I used to swear by Edge Gel till by buddy told me to try Nivea menthol and I haven't used anything else since. Also, take a wet washcloth soaked with water as hot as you can stand and hold it on your face for a few seconds before laying the gel on. It'll open your pores and allow your hair to move around without getting really irritated. Then when you rinse, use warm-cool water, not cold if you can help it. Then rub the aftershave on, if you're bleeding hold a towel around your chin/neck for a few min.
It works for me, the only time I get bad razor burn now is if I'm wearing a shirt and tie and it rubs on my neck.
Cheers