I've never heard of balkwalking. I'm not a fan of backwalking (first I've heard it called that) as they don't always know what they're doing.

it is a wonderful experience, and yes, a face cradle is a must.

 
But it can result in a broken spine if done by someone who doesn't know what they are doing, so it's not the type of thing I look for in an AMP, not that I've ever found an AMP gal who would do such a thing.

I'm not a big thick guy. Kind of skinny so it hurts.

Yes, I agree she has to know what she's doing.
I've had both good and bad, and you usually know right away which one it will be.

One gal's feet felt almost like fingers. And she popped my back a couple times between the shoulder blades. (My chiropractor can't even get that spot most days)

Time for a rub down!!!  Cherers!

I love the walking!  Some will also walk down the back of the legs, but stop at the knees.  When doing this it helps if the front of your feet are propped up on a towel, that keeps the legs aligned.

Slow steps, building pressure instead of striding to the next spot is a key measure in my book.  If they're fast then tell them to step off, but if they're slow it means we can test out their skills without surprise pressure.  Slow movers also seem to know not to step on the spine, but stay off to one side.

Some days, usually after flights, my back is so tight that it needs walking just to loosen up enough for feet and elbows to make a dent.  On those days I request specific ladies whom i know can do it right.