I thought I would kill two birds with one stone here, as my reply is really just a way to subscribe to this thread. I've ventured into the head shave for the first time just this week, so I want to see what people have to say, and advice given to the OP may well apply to me. I used to clip my hair from #1 through to #3 in a progression. I would always shave the back of my neck 'blind' with a DE to keep a neat hairline, so I thought I would try for a head shave this time around just for the hell of it.
I used clippers to knock it down as close as they could go before using a Merkur slant with an Astra blade to do the shave. I found the only issues I had was at the crown at the back. I just couldn't get it smooth. I had other places that felt a little patchy but they would be fixed with more practice I would think.
I don't know that I would have time to make a regular thing of head shaving. I think my practice will have to come over a longer period of time, with various hair lengths between head shaves. For the moment I'm chrome :)
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Mick