How to cover beads with spray acrylic evenly?

There may be other ways to do it, but here's the technique I'm familiar with. Slip the beads onto toothpicks, then stick the toothpicks into a styrofoam block. You can hold and twist the styrofoam with one GLOVED hand (don't turn it upside down, tho, or your beads will fall off) and spray evenly with the other.

If the holes in your beads are bigger around than the toothpicks, wrap a piece of masking tape sticky side out around each pick, slide your bead on and stick the inside of the hole to the tape. If your beads are too long for toothpicks, you can use bamboo skewers instead. You could also use any kind of florist clay or foam instead of the block.

Let the beads dry and re-coat as needed - multiple light coats are better than a heavy one. Save the picks and foam for next time - you can re-use them repeatedly.

Good luck - paper beads are so cool!