separating almond flour from almond meal
Any good hardware store will sell screen in a variety of mesh sizes.
Pick one out that matches your dome-sieve, and buy a couple square feet.
Make a wooden frame with say six inch sides, and tack the screen solidly to the bottom.
Sieve into a clean dishpan. Your sifting rate will increase substantially over what you're getting now.  

For really fine flour, head to the fabric store, or buy a pair of nylons, and frame as I've already described.