Also am a little worried about weight as my 2x4 trusses are 4 feet
aopart and I dont think designed for the wieght of a full ceiling.

I put up a 40' x 24' garage this summer, and insulated/drywalled the
back 16' for a workshop (so, 24' x 16'). It was a pole-barn style
building, with 4' trusses, but I was still able to drywall the
ceiling. We (my BIL, who is a general contractor, helped) ran 2x4s
flat every 16" crosswise to the trusses, and hung the drywall parallel
with the trusses. This seems to have worked pretty well so far, as
there's no cracking in the ceiling.

We also had 10' walls but my BIL ordered nothing but 8' sheets, and we
did all the sheets long ways along the walls. In retrospect, the
cutting involved with 10' sheets would have been better (after
dropping the inch and a half for the 2x4s, plus 5/8" for the ceiling
drywall, we were less than 10' to the floor). I did three layers of
mud, although I used the paper tape and the first two layers were more
"filler", with only the last one for smoothing. I was aiming for
"nice" but not "professional" - you can see problems up close, but
after painting, it looks ok from the center of the room.

Henry