Cliff notes version....
Start low... At or below start charges if known.
Work up till your feel light resistance on the bolt lift, then back off 5% minimum.
That would be your theoretical safe max load...
How detailed you want is up to you.
Most folks go half grain increments.
Change cases,bullets,ignition...lot numbers of propellent, start all over.
Your firing these for velocity and safety.... Not necessarily accuracy. That comes later once you know the safety margins.