I get the same problem too and Ive been using rescue oil and it look so much better. Ive always used the best razors, best shaving gel and they dont seem to make much difference but the rescue oil has done wonders
I was taught to shave dry using talcum powder. Used to take the back off the disposable razor to expose a very good Wilkinson Sword blade which was then used like a cut-throat. Yes, I am specifically talking pubic shaves. Have done hundreds of people like that and never had a problem.
When shaving, shave downwards rather than upwards. If your using a good razor, you should have very minimal bits left. Around the gentle parts you can shave upwards to get away any spikey bits. I never use shaving foam, mild shower gel and water. Apply a little vaseline thats is all after. Another thing i do is keep on top of it, otherwise youll repeated episodes of rash.