Closing the barn door after the horse leaves isn't the answer. If you get razor burn trying to treat it is difficult. I know of no product that will really treat moderate burn. The best product I can think of is Thayers superhazel.

Burn means damaged skin so you have to figure out what is causing it. I'd be willing to bet you are using too much pressure on the razor even if you think you are not. I've been using straights for years now and use a DE on a regular basis too and recently bought a Muhle R41 open comb and I'll tell you I thought I was using minimal pressure with a straight but using that razor has showed me that is simply not the case and I've had to reevaluate the pressure issue. You might also want to check the angle you are using.