Compression & leak down testing questions

A few newb questions:

1. FSM says to warm up the engine before doing the compression tests. I don't have tons of experience pulling the plugs with all the top end stuff attached, so I'm afraid the engine may be pretty cool by the time I get #6 out… how warm is "warm"? If it takes me 20-30 minutes to pull the plugs (yeah, it could), and another 5 minutes per cylinder, I'd be close to an hour before getting to #6. That doesn't seem too long to me, but just wondered…

2. Assuming I find a cylinder with low compression, it raises several more questions:

• should I be doing the FSM procedure of putting a small amount of oil in the cylinder to see if that helps, or go straight to leak down testing?
• I've seen videos that show using a tool that gauges how much leakage you have, but I can't really see the benefit if I have already decided I have unacceptable compression. I'm mainly interested in knowing where the leakage is going. Is there another reason to use the tool? It regulates down the air pressure, so I assume that may be one of the benefits. I read online that using the tool can indicate variability in leakage from one cylinder to the next, and the gauge indicates percentages which may be used to judge whether that's acceptable or not. The only reason I could see this being helpful would be if the compression test was not done first.
• If I use straight air pressure, would assume something in the 40-50 psi range should be enough… any advice?
• I've tried using compressed air once when I was removing the valve springs. I had read that was a way to keep from dropping a valve. I hand cranked until the piston was at TDC, but when I put air pressure on it, it moved the piston to the bottom of its stroke… thought I had the transmission in gear, so that was a surprise. It's been a while, and I may have done it wrong… just wanted to make sure that's the right way to keep the piston from moving… don't really know any other way, and it's what I've read as the procedure.

Thanks in advance for your continued patience with this 50-year-old newb… (well 49 for 2 more hours).