Best thing is to get them done in August  or September when it's usually dry enough that you won't be getting heavy rains and gives the grass time to get started before winter. This was a project a couple years ago along the road where the ditch had gotten humps in it over about 40 years since the road was widened and the ditch was made.

The fabric we used had long wood fibers instead of straw with plastic mesh. Work your ground, sow your grass seed then roll out the fabric and pin it down. We used the round top pins as well and had long sticks with magnets to push them into the ground.

I've since helped install this on several thousand feet on other's waterway projects using the same material and it has always resulted in a great stand of grass.

I was skeptical about the pins. But the round top keeps them from being pointed and they are supposed to just rust away over time. I've had zero issues with the plastic mesh or the pins. You just want to make sure when you are finally able to mow that you don't cut the grass too short and get into the mesh.

The guy that did my ditch got the rolls of netting with wood fibers. If you have lots of area consider maybe suspending from a loader bucket or pulling roll with 4 wheeler. Definitely use magnets on handles for pushing pins in.

Here are some with straw

http://www.strawblanket.com/

This place has various types.

http://www.drainagesolutionsinc.com/products/erosion/blankets/indexview.asp