Most efficient: Seat and crimp separately
In a 550, set up for .45 ACP:
Station 1, resize and deprime on upstroke, reprime on downstroke.
Station 2, bell the case mouth as little as will work for your bullets, and drop powder.
Station 3, seat bullet ONLY. Back out the die to where you're barely removing the mouth bell as you seat the bullet to exactly the depth you want.
Station 4, crimp ONLY. If you're lusing another seat/crimp die, then back the seating stem well out so you don't disturb the already-seated bullet. If you're shooting the .45 ACP in an autopistol, use a taper crimp. If you're shooting them through a revolver, then a roll crimp is okay, but don't mix these up with ammo for an autoloader.
Since I have both autoloaders and a 1917 revolver, I taper crimp everything, except for .45 Auto Rim. No danger of chambering an AR rount in a 1911.
Best,
Johnny