Harmonic
Tele-Meister
Cut a piece of tubing from something and start playing. Iron, PVC, copper plumbing work well. The 2nd, 3rd and 4th strings on a guitar make an open G chord, play notes there. When playing slide you can play a little flat - that's OK - but sharp doesn't sound so good. You can raise the strings at the bridge, it's reversible. It does not matter what kind of guitar you use.
