I don't know if this will work for everything but it's something I tried and it worked.

I've had trouble sowing fine seed like nicotiana because I can't see where it goes on the mix.  I had a Bounty paper towel disintegrate from being in water and I also have put them in the bottom of pots just to keep the soil fromsifting out.  I thought I'd try something.

I had lots of Nicotiana "Red Bedder" seed and a small flat.  I cut a piece of paper towel that fit the flat and seperated the two layers; then I wet the potting medium and the toweling and pressed it down lightly.  I sprinkled my seed on the white toweling and covered it with plastic wrap.  Maybe I could refine this a bit (try making grooves or something) but the seeds have germinated and look healthy.  I guess they were strong enough to go through the toweling.  I got the "Red Bedder" from Select Seeds and you sure get a lot of them.  I never grew that variety before. 

I would have tried it with coleus if I'd had enough and had though of it in time.  This would work with seeds that aren't supposed to be covered.

That's pretty cool.  Some of those seeds just disappear, don't they?