Assuming you are using polylocks
and not factory rocker arm nuts
which are not used to adjust your lifters to zero-lash - they get torqued down only.
You can use the static (engine off) hydraulic lifter adjustment when you first install a new cam/lifters just to get the adjustments withing running specs. I would not adjust my lifters/valves if the engine was not running. They bleed down over time depending on the position of the cam, so some will be bled down while others will remain pumped up and not a good way to adjust the engine.
I feel that the final and most accurate method of adjusting hydraulic lifters is with the engine running. Get the engine up to operating temperature so all the parts are expanded to the dimension that they will be operating at. Adjusting the valves with the engine running is more accurate than when the engine is stone cold and you hope you don't over tighten something and cause damages. If you over tighten, you could bend a pushrod or a valve may hang slightly open and you'll be trying to figure out why your engine is running so poorly or acting up.
1. Let the engine tell you when there is excess lash by slowly backing the polylock nut off until you can hear it - Tick,Tick,Tick
2. Let the engine tell you when the lifter lash is zero as you slowly tighten the polylock nut - Ticking stops.
3. Wait about 10 seconds for the lifter to bleed down/normalize and listen. If no more ticking, then got to step 4. If ticking returns... slowly tighten up on zero lash again until the ticking stops. Repeat as needed and give it a few seconds to normalize each time until the ticking stops.
4. Once the ticking is completely gone, your lifter is at zero lash. I then tighten the polylock 1/4 turn more and lock the allen screw down. You are now good to go and you can button it up.
This method will get messy. I use a clip which fits on the rocker arm (stock style) which covers the oil hole so the oil does not spurt all over the engine. Some use an old valve cover and cut open the top to expose the rocker arm nuts, but cover the rocker arm oil hole and keeps the oil from spilling onto your exhaust manifolds. This is probably the best way to go, but I like all the smoke coming off my exhaust manifolds which speeds me up in getting the job done as quickly as possible and praying the oil doesn't catch fire on the hot manifolds - which pumps up my old age adrenaline glands and excitement levels by a factor of five.