I use the RCBS Uniflow powder measure for everything, which means I have to thoroughly clean it between powder types.   I normally use Bullseye and Unique, both of which leave a lot of residue on the inside of the powder measure hopper.   Since the hopper is not easily removable, I came up with a way to clean it.   I started thinking about how we clean the inside of gun barrels and it struck me that the same idea should work for the powder hopper.   I took a 1/2" dowell cut to about 14", cut a slot in the end about 1/8" wide and 2" long, and slightly rounded the end with a sanding disk.   A normal paper towel is about 11" wide and 10 1/2" long.   Betty found some paper towels which were serrated into sections about 1/2 of a normal paper towel (11" wide and 6 1/4" long).   On one of these small sections fold on the 6 1/4" side then double three times on the 11" side so the result is about 3 1/8" X 1 1/4".   Insert the center of the 3 1/8" side into the slot and it makes an excellent swab to get the loose powder out (just like a gun barrel).   I then wet another paper towel section with alcohol and swab out the powder residue.

BTW #1, if you ever do replace your hopper, it is a press fit, so I used a strap wrench (sometime called a web wrench) and it came out ok.   To replace the hopper, place it on the top of the powder measure flange, place a wooden block on top of the hopper, and gently tap on it with a mallet to seat the new hopper.  

BTW #2, I use the hopper baffle in my Uniflow to even out the pressure so it throws a little more accurately, and one of the problems in cleaning the hopper is removing the baffle without spilling powder all over the place.   So I came up with a baffle puller, its just a piece of 12 ga. copper wire with a hook bent to a little sharper angle than the hopper is so it'll lift it straight.   Please see the last pic.

Slot cut in "cleaning rod".   You can see the powder residue at the bottom of the hopper, you can't get it all out but this cleaning sure improves things.

Large and Small Paper Towels.

Folded Small Paper Towel ("patch").

The "patch" inserted in the cleaning rod.

Cleaning Rod In the Hopper.

Baffle Puller   I use this to pull the baffle out before dumping the powder and cleaning the hopper.   This is just 12 ga. copper electrical wire bent as shown, but it works great.   Just push it down into the powder in the hopper, twist it slightly so the hook catches the baffle and then gently lift the baffle out.