I need to make about 50 or so blanks.

I do not want to use Black Powder, or any of the BP substitutes, but some smoke would be good.

I have a decent selection of fast and medium powders.

Your suggestions appreciated

Find someone who sells or has EC Blank powder, won't take much for 50 rds.
EC blank was or is the fastest burning of the smokeless propellant That powder and a waterproof cap over the case mouth to hold powder in case. IIRC the old Pineapple grenades of WW2 vintage used EC blank powder?

Jeff had some that at GI Brass a while back, but it was 8# containers as I remember.

They had a big caution to not . . . NOT load any type of projectile.

How many gazillion rounds would that load.

Roughly 10K per lb. Depends on how loud a bang. Start with 1.5 gr. and go up around .5 gr. until satisfied. Go slowly.

Most quick burning powders, work pretty well, look at enlarging the flash hole to prevent primer back out. A light wad of paper or even paraffin, can serve as well. do not compress the powder with the wad. I used to use a light card stock cut with a case the same size, by belling the mouth of the case, sharpen the case mouth by chamfering the case mouth. After priming and adding powder, set the wad into the mouth of prepared case, hold ii in case with a drop of paint, when dry finish case with enough crimp to ease feeding into the chambers. It worked okay for me. I used Bullseye powder, adjust a bit for noise results. Be safe and stay low on charge. Just saying. Good Luck.

Ain't worth worth the time to me.
I buy mine at Atlantic Wall Blanks. I use the theatrical loads for my shooting demos.
Lot of noise,fire,and smoke! They are smokeless powder loads. I like them and at $18.99 for 50 rounds the price ain't bad.

http://www.atlanticwallblanks.com/38-REVOLVER-BLANK-FULL-CHARGE-SMOKE_p_145.html

"The Mad Bohemian"

Atlantic Wall Blanks also. The theatrical full loads.

http://youtu.be/rBwGOfORUTQ

"The Mad Bohemian"