I shave my head every time I shave my face and my favorite razor is an old Schick Injector. At my age, it was time to give up the past glory of hair. So now I save big money on shampoo and hair cuts!

I personally don't think I get any more nicks on my head than I do on my face which only happens if I get clumsy. That said, It DOES take some practice.

I did try all the razors in my small collection and even Bic 2 blade disposable, (there ain't no shame in it if it works for you). My favorites are the Injector, my Slim Adjustable, a Lord L6, and oddly enough, a copy of single edge 3D printed razor I downloaded from thingiverse. (look up the Stoll JR) I did need to make a longer handle for it though.

I found I like lighter weight razors with longer handles for head shaving. But a good slick and cushioning lather matters just as much as the razor and blade. I use Arko stick for soap because it makes the best lather for me period.

As far as technique goes, the same rules apply to head as your face. Take your time and go slow. I find that for me, my head shaving got so much better when I figured out I needed to "Use the Force Luke". I literally close my eyes and just shave. No stress and no worries.

Head shaving with a safety razor does need to end up in a bloodbath. Just take you time to learn and remember: It's all a YMMV thing.