I have sensitive skin as well, and I have found it has a lot to do with the blade. I am a very hairy guy and usually trim all body hair once a month. For me, Micro Touch SOLO blades are the best foil shaver for sensitive skin, and shark blades give me a smooth but effective shave. I am really like this shaver. It definitely does not get as close as a straight razor it's awesome for a quick shave for my face.

On my fat boy, I use a 5 setting on my face, and a 3 on my neck, which is my troubled sensitive area. Also, some people just can't shave against the grain, their skin is too sensitive. I have also found an alum block after my shave greatly reduces if not eliminates razor burn. I hope he finds the right combo, razor burn is the worst.

I have loved my Weishi Long Handle adjustable butterfly, and the Weishi blades that came with it. Adjustable razors are a great option I am finding, first, pass I have it set at a 5 and then dial it back to a 4 for second pass cleanups. 

Haven’t suffered a single nick from it in over 3 weeks of shaving. Only a bit of burn I feel with the aftershave occasionally.

We all have our favorite blades. I would recommend you get a sampler with a variety of different blades. And see what works for him. For me, a good smooth shave is with the Personna Blue Lab. I also agree with the above - no pressure on the razor - let the blade do the work. And use an alum block, it will give feedback. 

One does need to develop a technique that works for him. For me three passes: north to south, across, then south to north. A pre-shave and a post-shave balm will also help.

Either way, irritation is not an issue for my skin.
Source: Upshavers website