The first video technique I referred you to was awful for your problem..too much fretting....and too sophisticated a style.

Take a look at this "Open G" tuning page - and its relationship to "dulcimer style" related instruments....(the kind kids can make and use) Note Mr. Robert Johnson and Bo Diddly references:

http://www.t4p.com/blues/opengslide.html

Playing the guitar flat on your lap or a low table is easy on the wrists. You can grip the slide many ways - whatever has the least pain. Think "country steel" style.

Sincerely,
Gargoyle

Highlandman - you are right - hammered does have lots of wrist action.