The same method should still work. The only difference is that the action command now requires you to repeat the name of the unit a second time, as a second parameter. It should look like this:
myUnit action ["TOUCHOFF", myUnit]
The remotely detonated satchel is still called pipeBomb. And if I remember it correctly the timer version of the satchel is called timeBomb.
EDIT: Destroying large quantities of map objects was discussed here a few days ago in
this thread. Unfortunately the two participants didn't share their mutual solution with the rest of the world
, but if they do I'm sure the same techniques that apparently works on buildings could be used on trees as well.