I use a multipurpose compost in shallow rectangular trays, and find
that it's well worth sowing any seed large enough to pick up
individually, at regimented spaces at least an inch apart in all
directions. (Cerinthe and basil, for example, are easily large enough to
handle). It is a little fiddly but quite quick, and not nearly as fiddly
as trying to separate clumps of minute seedlings. Larger spacing gets
seedlings off to a far better start imho, because they can get nicely
established roots, without becoming drawn/skinny, before being potted
on. Also, it's easy to identify emerging shoots from the spaced seeds;
any which appear in the wrong place are most likely weeds and can
easily be tweaked out.

Most people have found themselves struggling to accommodate/care
for/offload thousands of seedlings of one sort, when they only needed
10, or 100. Individual spacing of seeds helps eliminate that.

Janet.