How can I sow grass seed on a 60 degrees slope?

The banking is fine dry soil and the seed just slides to the bottom. I've gently sprayed the soil with water, but when the soil drys in the sun, the seed slides down again.

If it is not a huge area to cover, sprout your seeds on level ground on triple sheets of newspaper. Once they have roots into the paper, you can pin the sheets down on the slope, with rocks or chicken wire, until they root through to the ground.
This would also work with other groundcovers, which,as Mbmruffian suggests, might be more suitable than lawn grass.

Stake chicken wire over the bank - peg it in firmly. Then mix the grass seed with general purpose compost/top soil and sand and sow over the chicken wire. Tamp it down gently and water with a fine spray (or lay a seeper hose over the area) and the seed and soil will stay put within the mesh. This will help to stabilise the bank too. Good luck :-)

Maybe you could spike the area first and mix the seed with compost. Spray the spiked area then apply the Mix. Fine spray the mix when it's laid and when it dries roll it to compress and break open the seed. Spray again. You could also cover with opened bin bags for a few days just in case you get a downpour.

You need to mix the seed with a general compost.. not a rich one or the seeds will burn. If you have another lawn area, save the mowings and spread them over the newly sown seed. Give it a good watering and the weight of the mown grass will hold the new seed and act as shelter too.

A 60 degree slope is pretty significant. It is not safe to mow. I would try a ground cover that has an extensive root system that can hold the slope up. Then you don't have to mow it.

use hay to hold the grass seed.... just spend it around and the hay will hold it. then after some grass grows the hay will rot and then you spend more grass seed.

these are great ideas but if its too time consuming
have someone come in and spray grass on the hill