I like to cheat and run everything through Load From a Disk. It will get you pretty close, but it's still helpful (and smart) to use Dean's method as another reference point. Once I get a basic starting point I load up one shot each at different powder charges in either .3, .5, or 1.0 grain increments depending on case capacity. I usually load up a total of 10 rounds. Then it's off to the range with a chronograph. Shoot the different charge weights over a chronograph and watch for pressure signs and changes in velocity. When the increase per grain starts to drop, you've hit the point where your efficiency is going down. Here's an example:

270 RUM with 140gr Nosler BT and US869 powder and a Federal 215M primer. I came to the conclusion that 86.0 grains would be a safe starting point. I started there and worked up in 1.0 grain increments up to 98.0 grains. When shooting over the chronograph this is what I got:
86.0 grains 3189 fps
87.0 grains 3254
88.0 grains 3315
89.0 grains 3383
90.0 grains 3447
91.0 grains 3505
92.0 grains 3566
93.0 grains 3598- slight ejector mark starting to show, primers starting to flatten
94.0 grains 3637- lite ejector mark, primers flat almost to the edges
95.0 grains 3677- well defined ejector mark, primer flat MAX load tested

I took this info and went back to start working up loads to test accuracy. I started at 92.0 grains and worked up 94.0 in .4 grain increments shooting 3 shots at each charge. The charge I ended up with was 93.2 grains at 3610 fps and .5" groups at 100 yards.

I've use the same basic test in all of the wildcat's I've worked with.

Andrew