Scraping undercoating is the worst.

[GoodysGotaCuda]

I used a knotted wire wheel on an angle grinder with a respirator. It made an enormous amount of dust, but worked pretty well

[1 Wild R/T]

Steam cleaner is your friend....

http://board.moparts.org/ubbthreads/ubbthreads.php/topics/1345552/undercoating-remove-it-or-not.html

[rhamson]

Nasty stuff.

I myself avoid it as much as possible.
I stripped parts using it outside only.

http://www.doityourself.com/stry/usingpaintstrippers

I agree a good whiff of it can send you reeling. But in a well ventilated area it works a lot easier and faster than the heat and scraping.

[bobs73challenger]

Update: Making progress! Wire brush drill attachment is working great. Having some trouble in some of the tight areas. Time to break out the chemicals.