In reply to Oceanrower:
The work harnesses (like Aveo) are comfortable... but not really suited for climbing.
If you want to get a harness that is comfortable to hang around for long durations and still be able to climb with them, have a look at real aid climbing harnesses.
Something like Ocun WeBee Quatro (or what ever is was called) felt really comfortable and not too restrictive whilst actually climbing. I'm used the WeBee 1 as my winter harness until I won another suitable harness from a raffle... so the WeBees will be used this summer for rock...
That said, the bosuns chair is the real way to go. Either buy, or DIY. Remember to still wear your harness whilst sitting in the chair and that is actually the primary safety you're on. The bosuns chairs is just above with a simple prusik, and should the prusik for the bosuns chair fail (or the chair), you'd simply drop a small length to your selected belay device (and perhaps a backup).
My normal "filming" belay device is a GriGri (and a fig. 8 on a bight is the backup), 'cause with just one ascender I can quite easily ascend the rope to a new filming position...