I use a poster board with the 4" "shoot n c" stick on targets, one for each group/charge. At 100yrds, they are easy to see(many of my rifles are open sight)
So for example, if I have a start of 25g and a max of 27g, I will run my first test at .5g increments;
25
25.5
26
26.5
27
Five or six rounds at each charge.
I take the best group of those five and I load 5-6 more at .3g below and .3g above that best groups charge to see if I can dial it in closer.
Anyway, that's how I do it, a poster board, some stick on targets, .5g increments from min to max, and 5-6 rounds at each .5g increment. Then dial it in with .3g above or below that best group.
It works for me, everything I own is MOA or better, including my Mini 14. I live 5 min from my private range that I belong to so two trips to dial in a load isn't a huge inconvenience for me.