How to measure and transfer suspensions?
Stir the dilute suspension rapidly, e.g., using a magnetic stirrer. Let a  vortex be generated whose size you can use as an estimate for vigor of stirring. With the same mixing vigor, and using the same size vessel and same original volume for the suspension, and withdrawing only a small portion (say, ~10%) for the other container(s) should enable fairly repeatable measurements. 

For obsessive accuracy, you could do three withdrawals: #1 for reference, #2 for experiment, and #3 for reference. If #1 and #3 show the same concentration of solid, #2 will certainly be the same, and the concentration will be verified while sedimentation will be proven to be absent.