Bottom Watering Help

When you bottom water seedlings (I'm using 1020 trays) how deep do you pour the water? I've seen sources say 1/8th inch all the way to half an inch.

Then, do you pour off the extra after a certain amount of time? One source said they pour off the extra after 30 minutes, other sources don't mention checking back on them at all, I've seen some people say they give it five minutes total.

If I'm supposed to pour off the extra (at say... 30 minutes) what if I check back in 10 minutes and all the water is gone. Does that mean I poured too little? Do I pour more and come back at the 30 min mark?

I am the worst plant waterer on the planet. I drown them or starve them.

If my seedlings were people I'd officially meet the criteria for a serial killer. I googled.

Dumb it down for me, please! Help me save these plants from myself.