Here's what I do, for .41 LC, inside lube bullet with BP.
If it sounds long-winded, it's all in the typing.
As always, mileage may vary, feel free to use or ignore any or all of the following.....
Lube bullet with SPG (or other BP soft lube)
Wipe excess out of hollow base.
For measuring BP amount.
Measure length of bullet to go into case for correct seating depth,
(use dial caliper stem that sticks out of end of caliper; stand bullet on caliper end next to stem pointing up)
Stick caliper stem into case & fill with BP (tap case to settle powder)& add BP until it touches the end of the stem. (end of caliper resting on case mouth)
Add BP compression depth worth of powder (about the thickness of a nickle).
Take a bullet, turn it base up, fill hollow base with BP to get amount to fill it & then pour it in the case.
Now you have the amount of total BP needed.
Adjust your measure to throw that volume of BP.
This will ensure that you have no air gap & good compression.