What substrate to put with seeds when overseeding?

Hi, I was in dobbies and looking at the things I will need when I overseeding my lawn in a month. My question is, when I seed, What should I put down on top of it. These are the two candidates I found in dobbies. The dressing one felt quite sandy through the bag, I think it's sand with a bit of topsoil mixed in.

 

Wont that make it much harder to keep the seeds moist if a number of them are exposed? Not to mention the birds.

 

I sow some extra seed for the birds, much easier than all the rigmarole trying to keep the birds off and I've never really found them to be a significant problem here, except when they use a seed bed as a dust-bath and then there is no seed left in that hollow :( Watering regularly, until germination, will fix that problem (and its probably not a problem with overseeding anyway)

 

I use sand, just because I like sand and moss doesn't.