Well, here’s a handy tip: use a saltshaker!
Mix the seeds with 2 teaspoons of fine sand, pour the mixture into a saltshaker (please remove the salt first!) and shake the mix evenly over the area to be covered. Since sand is paler than moist growing mix, you’ll be able to see if you’ve missed a spot or two.
Such fine seeds don’t need to be covered with soil, so when you’ve finished applying them, just spray the tray with water and you’re done.
Come germination, you’ll be surprised at how evenly the seeds are spaced.