Pick one powder you want to try, look in the book to find a starting powder load, work up at .5 gr increments(at least 7 or 8 times), go to the range and shoot to see if you can get some good groups. If you find a couple that shoot well go go home and load up 2 groups worth of each powder that shot well, then go back to the range and confirm groups. If you didn't find any good groups that shot well switch powder and redo the whole program. Some guns are picky with powder, if you can't find good groups with the bullet, switch bullet and start the process over some guns are picky with bullets and bullet weights.
Example: Starting with H4831sc at 65gr with 168gr berger..
Load up 65gr, 65.5, 66, 66.5, 67, 67.5, 68, 68.5 > 3 shells for each powder weight
Go to the range to find out that 66.5 and 68 gr shot 1/2 inch group
Go back home and reload 10 rounds of 66.5gr and 10 of 68gr, then go back to the range and fire them in 5 shot groups and find out which is your best powder weight to use. Then start fine tuning your load. Or you may find out that your gun doesn't like that powder. So switch to a different powder
You can't find out much by only loading up 3 different powder weights of a powder, you may get lucky but you may also not see that great shooting group your looking for if you don't play with enough powder weights