Paint Mixer directions:

Bottle Holder
We are going to put a total of eight holes in the 1 1/2" by 1 1/2" by 6" maple block.    The first six holes are for the bottle caps. (all the same diameter and depth) the first hole is located on the C/L of the block and 3/4" from X and 1" from Y and 13/32" deep.   Bore a blind hole to have a tight fit for the cap of the bottle. Mine is 1.094" Diameter.

The second hole is located on the C/L of the block 3/4" from X and 3" from Y.   The third hole is located on the C/L of the block 3/4" from X and 5" from Y.   Turn the block over 180 degrees.
Repeat the location, and dimensions for the fourth, fifth , and sixth holes.   Now set the block upright in a good vise.   Use a good square to make sure the block is perpendicular to the machine spindle you are going to use.   The first hole is on the C/L (centerline) of the block.   That is 3/4" by 3/4" from the X and Y reference edges of the block.

Bore a close fitting hole for the 3/8" shaft by 1" deep.   Now just turn the block over.  Set it upright as before.   Go to the C/L of the block and drill the close fitting hole 3/8" by 1" deep.   The bottle holder should be lightly deburred and sanded to remove all sharp edges.

Shafts
Take some Aluminum Bar stock and put it in your three jaw chuck.
It is advisable to machine both the .375" Diameter and the .316" diameter at the same time for concentricity.  So, have the stock about 2 1/8" long from the front of the chuck jaws.   And the stock has to be larger in diameter than the .375" dimension, say 7/16" Diameter.

You can use .375" Diameter by putting it in a four jaw chuck, and truing it up using a dial indicator, and then turn and fit up the .316" diameter to the inside diameter of the nylon spacer but I felt that might be beyond the skills of most, even if you own a lathe. :)

Turn the .316" Diameter by 1/2" long first, carefully fitting it up to be a medium push fit with the inside diameter of the nylon spacer.
Next, turn the .375" diameter by 1 1/2" long to 1 9/16" long
to allow stock for cutting it off and leave material to face off to length. Fit up the .375" Diameter as you turn it for a medium to heavy push fit for the .375" Diameter holes in the end (s) of the Bottle Holder.

Cut off the shaft , turn it around, and face it off to the 2" long overall length of the shaft(s).  Break all sharp edges, and put a slight chamfer on the ends of the shaft(s).   Now, repeat for the second shaft.