I'm surprised at just how common an issue razor burn seems to be amongst us! I sincerely get as close a shave as is possible without shaving the top layer of skin off yet I never have razor burn. I mentioned this before but one thing I learned involves shaving any part of your body with loose skin or worse, loose, wrinkled skin! I stretch it out taught by grasping a section with my left hand while giving the quick few swipes with my right. Whenever I've been lazy and simply tried to get the few hairs without pulling my skin taught, I've bled, and paid for it.
For what it's worth, I use one of those Gillette "FUSION" battery powered razors with the 5 blade cartridge that also has a single straight razor on the back. I learned how superior these are compared to standard razors when shaving my head as it's superior insofar as closeness and speed. The fact that it vibrates indeed does seem to make a difference as well, especially in "sensitive" areas. I use standard issue Barbasol shave cream though I shake the can vigorously for 5-10 seconds as this makes the foam much thicker and a little goes a long way. I shave, or I should say I "touch-up" down there at least every 3rd day at the extreme maximum. I have to shave my head every other day at the maximum though with how busy I have been this summer (despite how limited I have been due to my horrific back!) I've needed to shower just about every single day, sometimes twice, and it's a rarity for me to not shave my head as it's so much faster and easier IF I shave before hair begins to become long enough that you can "feel" it when your run your palms across your scalp. I usually "touch-up" downstairs at the same time as i have the shave cream and razor already in use, so why not?
I don't know if my skin is more resilient than others, if the razor and shave cream I use makes that much of a difference (Barbasol green can...menthol-ish? Honestly can't recall and my shower is upstairs so....) but unless I'm rushing or just plain not paying attention, I have no issues. The worst I deal with is the occasional cut and bleeding. The bad is that it hurts and is a bad are to have ANY wounds. There is some good though, as it really makes you regain your focus when shaving for at least as long as it takes any cut to heal LOL.
I have also never dealt with severe diaper rash despite wearing for 20 years now, including being asleep for over 20 hours in the same diaper & booster pad. I'll occasionally get an itch, but it seems as soon as I either am cleaned up well OR I am able to shower, the itch is gone and my skin is pretty much unharmed. WHEN I know there's a good chance of me being asleep for far in excess of the 10-12 hour range I always apply a fair amount of the Triple Paste, which is the thickest rash preventative/rash cream I have found, and it must be doing something right!
I do know that if you repeatedly try to shave the same patch of skin more than once or twice, that's when you're likely to experience razor burn! I learned that with my head. I'll get a bug up my ass and insist I can feel hair on the upper part of the back of my scalp...not an area easily seen while showering and I was repeatedly trying to shave it so that I couldn't "feel" any hair. Yeah! RAZOR BURN, more than slightly aggravating a couple of times until Learned that if a couple of good passes didn't remove it, it's likely not there OR will live until the next night when I shave my head again. I also know that touching up every day or every other day RADICALLY reduces all chances of razor burn as you're able to shave so quickly due to next to no hair being in existence and I've never experienced razor burn down there except when I let it grow for whatever reason and then had to "get the weed-wacker out" LOL. When there is a lot of long hairs, you truly are better off trimming it really low one day and then shaving it clean the next. Shaving full grown pubic hair is an exercise in futility! Your razor is CONSTANTLY clogged, the shower drain does an amazing job collecting everything no one wants to clean up and the hair turns your drain into a pretty functional dam and it takes an hour to finish the job....not to mention that there is no way you're NOT going to be "punished" for the stupidity of doing what you ought to learn from the 1st time you ever tried this 25 years ago!
I have no idea if what works for me will work for anyone else. I have zero issues, so long as I don't break any of my "rules" which of course I do as I wind up in a hurry. Is what it is I suppose!
CptKirk