How wet is too wet of ground to plant grass hay?

We've killed the hay field, and tilled it twice at 4 inches to break up the hard pan clay. Has been hay field well over 20 years by previous owner,with minimal care.

Plan to plant pure orchard grass.

Question : how dry must the soil be before planting? Boss man with no experience says powder dry, no cultipacker.

Will plant using brillion style planter with microtiller on front.

Field has baseball size clay lumps in certain areas, especially wetter ones (tractor is leaving tracks). I'm thinking to field harrow it, then pack it and clumps will level off, rain forecast this weekend. I don't think it has to be bone dry, but that's why I'm asking.

What is best to prep for planting?

I do have pics, but not sure how to add.

How wet is too wet of ground to plant grass hay?