I'd definitely try without a grease wad first.  Using a grease wad would be a last ditch attempt to fix a leading problem.  This presumes you're using a grease bullet bullet of groove diameter or .001" bigger, with appropriate blackpowder lube in the grooves.

To load for any blackpowder cartridge with minimal bottleneck:

Drop a bullet down the barrel measure from the base of the bullet to the breech block.

Subtract that measurement from the case length.  That is how deep the bullet should seat in the case.

Pour in blackpowder through a drop tube (18 inches or so long) until it reaches about .2 inches (.4 for longer cartridges) above the calculated seating depth.  Experiment until you can do this repeatedly, then use that weight of powder from now on.

Put in a card wad on top of the powder.  Use a compression die, to compress the powder until the wad is at the calculated seating depth.  I use a seating die with a seating plug turned to a flat end with a slight chamfer.  You can use a flat face seating plug for a wadcutter bullet if that's all you have.

Thumb seat the bullet on the wad.  

This should seat the bullet just lightly into the rifling when you load the cartridge, which will give initial resistance to help burn the black powder.  With a high wall, you can actually seat the bullet a bit less by not compressing as much, and use the closing of the block to push the bullet into the throat/rifling.

You don't need to crimp, or for that matter even size the cases.  The bullet should just slip fit in.  If you have to size to keep the bullets from falling out, do so just enough to hold the bullet in, you don't need to have any neck tension on the bullet.

Loaded 16 rnds today with the grease. The bullets mic out at .4035 and are ~30:1 and SPG lubed. The bore, from the breech shows quite a bit of erosion etc. for the first 1/3 and from the muzzle it's nearly new looking for 1/3+.  I have had leading with smokeless loads.