The way that works best for me is to first pick the bullet I want to use and build the fastest,most accurate load around that.

I load three rounds of each powder I have on hand. 1 round at max load and one at 1 grain and 2 grains below that.
Then I go to the range and fire each powder type at a separate target.

I shoot the lowest powder charge first and the hottest one last of course.
This let's me see if there are any pressure issues, and it would probably start to show at thethird charge weight.
For the record I have never seen any of my guns show any signs of high pressure with any published load data.

I clean the gun after each powder.
This lets the gun cool down and removes any powder residue from the barrel.

I just loaded 12 rounds of 338-06 yesterday behind a 175 Grain X Flat Base.

With just 12 rounds (3 each of 4 different powders) I will be able to tell which powder the gun/bullet likes best.

Then I will load 12 more rounds of the winner and shoot groups to confirm the combination.
The accuracy is surprising even though they are 1 grain and 2 grains apart.it is amazing how close the right powder will group even at different charge weights.

If I don't get where I want to be (< 1MOA) I will either purchase some other powders to try or move to another bullet, But have never had to give up on a bullet yet. Primers have never been an issue, and I have had more luck changing powders than changing primers.