I personally use a Dunlop Brass slide for acoustic, was using a copper pipe I pinched off my brothers truck (he's a plumber) and the difference in sound is amazing.

Here's what I think, glass for electric, steel for acousstic and tune down to say DGDGBD and muck around in the Open, 3rd, 5th and 12th fret positions.

http://www.bigroadblues.com