I've been working on this for about a week, looking at youtube videos ( see the drop back playlist on my Youtube channel http://www.youtube.com/view_play_list?p=2BC774BEFFB4F372 )
At first I tried dropping back to the wall then walking down it. Had a few goes leaning back as far as I could to see how low I could go. Today I tried a couple of supported drop backs to the sofa(Thank You Misa) very disconcerting as it seems so far away. Next I put two large Sofa cushions on the floor and dropped back on to them. Felt Quite confident as I could see the middle of the cushions
Next I dropped back on to one Cushion. Still felt comfortable, although I could only see the far edge of the cushion . Seem to drop back a lot faster on this one, felt less controlled.
Finally with more than a little trepidation I tried dropping back to the floor. Very nervous about this as the floor was a blur on the edge of my vision. Takes quite a leap of faith but after the previous two you know the floor isn't as far away as it seems. (Apologies for the lack of a shirt but I wanted to see my back as I bent back).
The exclamation at the end is from joy and surprise rather than from pain.
Getting back up from the backbend seems a hell of a lot harder than dropping down into it.
CAUTION: I should probably point out that I've been doing Ashtanga for a year and a half which includes, what, three floor back bends, six days a week. Ashtanga develops the core muscles which helps prepares you for the back bend and drop backs. I guess I'm saying I'm coming to the Drop back with a fair amount of preparation and I'd strongly recommend you were suitably prepared too before you "try this at home".