Essentially razor rash is because you can't shave properly. Its not rocket science but seems to elude many men for all of their lives.
The trick is to use only a gentle, non-foaming oil or shave cream like the old days, on a nice & warm face. Only shave in the exact direction of hair growth- not rasping down against the grain. Your hair probably swirls all over the place, more than you think – side to side and up & down etc. If in doubt get a lady to show you the direction of your hair growth & go with the grain.
If you hate throwing blunt razors out then just buy cheap disposable ones & use less. This means they are sharper & don't have bacteria living in them.
The perfect compliment to your shaving routine is a little Magic Balm to cover the pores and protect your baby's bottom of a shaved face.