The name of the game is PRESSURE and VOLUME. You gotta take new socks and rinse them under full garden hose pressure for a good 5 minutes (inside and out) then final rinse with DI water.
Common manufacturing method for GSM materials produce a residue (though harmless) that makes protein skimmers over-skim immediately if not all the residue is shed prior to use.
Same method applies to used/dirty filter socks. Simply BLAST them with as high pressure of water as you can find (inside out) then shake off and dry. As a last resort, the "spray" feature on some kitchen sink faucets (also known as needle spray pattern) will rinse the material much more effectively then a standard stream. Try it and you'll see.
Running a show of 75+ booths/vendors, touch tank, frag tanks, etc. was bound to teach me a thing or two every once in awhile. Glad to share