Installing Hydraulic lifters in an engine and getting them pre loaded so You don't have to adjust at all after initial install is straight forward.
The problem is you get one shot at this. If you mess up you will be correcting the lifters with a running adjustment later. This is for adjustable rocker arms only.
You spin the engine till your #1 cylinder is on TDC, top dead center on the combustion stroke not the exhaust stroke. I like to start with Cylinder #1 and then follow the firing order around till all 8 are done.
If you start at #1 on a 4 cycle engine it takes 2 full revolutions to complete one cycle. So every 90* of rotation you will be adjusting one cylinder.
Have a sharpie on hand and mark each cylinder as you complete it. This way if a phone rings you can leave and come back knowing where you are.
So #1 on TDC compression stroke. You will be able to spin the loose push rods freely in the rocker arm. They may be super loose so you need to start tightening the rocker arm nut. Keep tightening as you spin the push rod with your fingers. Once the play is gone and the push rod stops spinning free you are ready to apply the Pre Load on the lifter. On New Lifters most would say to add 1/2 turn to 3/4 turn for pre load. Some say 1 full turn. All 3 should work fine but do all 16 adjustments the same. I usually go 3/4 turn.
Once you adjust the #1 intake and exhaust rocker arms turn the engine to next in the firing order and do the same adjustment before moving down the line and completing all 8 cylinders. Once this is done DO NOT adjust the rocker arms at all. They are adjusted and pre loaded. You are DONE. Any more adjusting just messes things up.
IF doing this same job with USED lifters on install do everything the same but for pre load only add 1/4 turn of pre load to the rocker arms.
This process is simple and fast but most importantly it works for setting Hydraulic Lifters.