I’ve tried it and gave up, although I don’t doubt that it can work.
What you’re doing sounds a little different – I didn’t go for a set six hours. The method I followed was to work out how much sleep you typically got in total, and start there. Once you stay asleep for the entire time (I have no problem falling asleep, just staying that way), you bring your bedtime forwards by 15 minutes. Equally, if you’re not sleeping, you push it back.
I gave up after a couple of weeks. My usual pattern at the time was to struggle through c.3 nights of awful (4 broken hours max) sleep and then get a broken 6 or so, which I could deal with. Although sleep restriction seemed to be working, neither I nor my job could put up with a fortnight of zombieism.
The doc suggested signing me off work. Maybe if I’d had a couple of weeks where I could zombie my way through the days with no need to function then I’d have had more luck.
I’ve since realised that my insomnia is a result of a bit of a whirlwind in my head and that it’s not going away until I get that sorted.
Trying to stay awake… I went for short walks, fixed bits of bike, played the keyboard with headphones in (any ‘hobby’ basically) or did puzzles as mentioned above. Best for me was watched TV or reading stuff that caught my attention – I know you’re meant to avoid screens but I’ve found that they make no difference to my sleep. I did try to wind down over the last thirty minutes or so though.
Different conditions and reasons for insomnia and I think it would have worked. Hope you have more luck!
Insonia’s fun, isn’t it?