Ok here is what I do when I build my shocks. I only use the V2 Shock now as they are smoother and don't have random leaking problems that some of the old v1 shocks had.
The first thing I do is not exactly necessary but I like to do it.
I cut the little nub that doesn't have threads off the bottom of the shafts. this makes me able to screw on the bottom and shorten the whole throw of the shock so the piston doesn't push on the bladder as much when fully compressed. Like I said its not necessary because you are probably never compressing the shock that much anyways but I do it none the less.
I make sure the white spacer that goes in the bottom of the shock slides on the shaft with no friction at all, I like to make sure it drops on. If it doesn't I hit it with a reamer real quick. But as of right now with the v2 shocks this problem has gone away and I haven't had to do it with the white machined piece.
I use the 40 degree o rings even with the V2 shocks all the time. I use green slime on the o ring.
I put a .2mm shim on top of the piston between the piston and the Eclip to take up the little bit of play the piston has.
As of late I don't like running any rebound at all in my shocks so I drill a hole in the plastic part of the cap right at the base of the shock mounting part that goes up from the flat part of the cap with a #57 drill bit.
Then I put the shaft in and make sure it slides up and down very very smoothly on the oring. It usually does if everything is done right. I ream out the shock bottom were the 5.8 ball goes in so it is as free as possible without any slop. This usually just takes a slight touch with a reamer. I also hit the plastic top with a reamer too, just so everything rotates smoothly.
I screw the bottom on as much as possible right before it starts binding the 5.8 ball in the bottom on each of the shocks.
Then I fill up the shock with oil. Always Losi oil, just because thats what I have used for the past 5 years so I know it well. And they have half weights which gives me more range of adjustment.
If possible I build my shocks and let them sit overnight and get the bubbles out, I don't like using a shock pump because it feels like you can always get bubbles to come up if you pump it too much. I do use them at the track once in a while if I don't have time to let the shocks sit for an hour or so.
When I am ready to finish I push the shaft 95 percent of the way in and push the bladder on with the back of my lunsford turnbuckle wrench or whatever is just about the same size as the concave part of the bladder make sure all the excess oil runs out and you keep the shock shaft pushed in 95 percent of the way. Then I screw the cap on almost all the way and push the shaft the rest of the way in as any excess oil bleeds out and then tighten the cap. If you drilled the holes right and built it right it should have no rebound at all and no contraction when you pull the shaft out.
I measure my shocks from end to end after being built and make them 61.5mm.
That is pretty much exactly what I do. The keys are making sure before putting oil in them that all the shafts slide on the orings very smoothly with almost no friction at all.
Also always make sure the pistons are clean and without burrs before putting them in.
I always use the 1.2mm pistons with 3 holes.
I think that is everything. Probably way more info than anyone needed and most of it unnecessary.