As long as they're the right size it shouldn't be too difficult. I usually place the lower mounts onto the axles and put the axle nuts on just barely to allow the trusses to still move. Then line one truss rod up with the top bracket and start threading the bolt into the rod. Don't tighten it much though, as this will pull the upper bracket in that direction and make it harder to line up the other side. Then thread the other side in a little, then go from one truss to the other tightening the bolts until it's done, then tighten the axle nuts down.
