I've been around planes mostly and was new to cars. I had a friend that was into cars and insisted the temp gun was the way to go. well I couldn't afford one so I broke mine in without one. I did it by ear. No spit and no gun.
When I got my motor it was way to rich. So rich, it wouldn't stay running more than 15-20 seconds. So I leaned it a 1/4 turn and started my heat cycles. I ran three tanks that way and after that I listened to it from idle to half throttle. If it was trying to go faster at half throttle and if I felt that the richness was holding it back and I could still hold my hand on the head then I leaned it out an 1/8th turn and never more than that for a tank till I got to about a 1/2 gallon and then started going a little over 1/2 throttle to around 2/3-3/4 throttle and still listening. Also if it was sill running cool with lots of smoke after after a half gallon I'd give it full throttle for a 1/2 second and if it still bogged real bad I knew I was rich enough.
Somewhere around 3/4-7/8 I started to race tune it and it was broke in. When I took it over to my buddys place and had him put it on his gun it was running a consistent 235f. and strong. So strong that I took out three three drive axels on my first bash session amongst the other parts from bad landings.