I've been shaving for about 5 years, and have been using a DE safety razor since August '16. I've developed my technique and have tried practically every variable I can think of. I've tried shaving with the grain, accross grain, against the grain, one pass, two pass, three pass, cold water, hot water, post shower, and pre shower. I'm still trying to find the best blade brand for me as I purchased a DE sampler pack from WCS. I seem to have very sensitive skin as I constantly find myself getting razor bumps (ingrown hairs) despite using as little pressure as possible and top of the line blades (Astra has seemed to work the best so far). I also find my skin is constantly dry despite using a post shave balm liberally from Sterling Soap Co. (I also exclusively use their shaving soap). I find that i get slightly better results when I use their menthol based or non-clove based products. My shaving routine typically consists of rinsing my face, applying a neutrogena charcoal face soap, leaving it on for a few minutes, rinsing, applying olive oil, taking a steamy shower, washing my face again with the same face soap, building and applying lather to a dripping wet face with my Omega boar hair brush, (to where I can lift the hairs up and then I apply extra soap to get a good coat) then I shave one region at a time with the grain (according to a grain map I made), holding my razor from the far end with as little pressure as possible, small strokes, not repeating an area. I also reapply to areas right before I shave them. I save my neck for last as it is the only real sensitive area. My razor is a Gillette DE black-resin handled safety razor my grandpa used and I'd guess it's probably a late 60's model as that's what I've seen in other videos (yes I've thoroughly cleaned it). The only thing I can think of that I haven't tried is getting a new safety razor that is know to be less aggressive. Any feedback is welcome as it is torture and I'm only able to shave once or twice a week otherwise my neck is plagued by those devilish bumps for weeks on end. I also try to lift ingrown hairs with tweezers when I can. My post shave routine consists of dabbing the cream away from my face with a cool washcloth, patting dry, applying witch hazel, and a styptic pen to any nicks. I then let it dry and liberally apply Sterling Executive Man post shave balm. Another thing that I haven't tried is getting an allum block.
Grow a clean beard.
I had a problem with this so I quit shaving them and used a comb and clippers and left them fairly short to avoid the in grown hair problem. I grow a beard so it really didnt look horrible. I can't explain why but the problem went away and theres a lot more hair on the neck now than then.
Damn I only do one pass with the grain, perhaps a second in my throat area. That is every week day. I take the weekends off. I change my blade every 3 shave days or so.
I wonder if you are over doing it. I'm a blond so any stubble is hidden to some extent.
Try the alum block.
I had the same problem in college but outgrew it. I think my hair got coarser over time so it would just poke right through the skin and not curl under.