I use the pre-cut blocks for regular truss layout and don't stress about layout much, it usually stays close enough, and it's quicker to just lap or gap a sheet than have two guys waiting while one is cutting a special block. We always gap our roof sheathing, so we end up cutting a sheet here and there anyways..no bigggy, just lap it and come back later to make all the cuts at once (yes even with H clips).
The only plate layout I do is for girder trusses or other specials, like drag trusses. I try to do that before anything is sett on the plates.
Before we climb up to set the trusses, we try to have all blocks and backing cut and hanging in the location it's needed, on (usable) nails just under the plateline, so you can reach it easily from the plates, but they're not in the way of walking and sliding trusses around. This is all done from the floor while the truck is unloading and setting bundles of trusses on the plates.
Walking back and forth in trusses and climbing up and down from the plates is a huge time suck, so the object is to complete the stack with one trip across the bldg. That in and of itself makes the job challenging and fun..and fast. We don't get to cut roofs as much as we used to so we just try to make the best of it.