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Planting time will depend on the type of grass that you choose, usually.

Generally, planting after the last frost in Spring is ideal for most.

Preparation will be similar to preparing a vegetable garden. This article will help:

https://www.gardeningknowhow.com/edible/vegetables/vgen/veggie-garden-winter-prep.htm

This article will help you to plant ornamental grasses:

https://www.gardeningknowhow.com/ornamental/foliage/ornamental-grass/sensational-borders-with-ornamental-grass.htm

Generally, grasses for shade can be difficult to come cross.

There are a few things that you can try, but you may have better luck with a different plant. These articles will offer some suggesions:

https://www.gardeningknowhow.com/ornamental/foliage/purple-fountain-grass/over-wintering-fountain-grass.htm

https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-8/zone-8-shade-tolerant-evergreens.htm

https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-8/zone-8-ornamental-winter-plants.htm

https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-8/zone-8-ornamental-grasses.htm

You can keep them in an unheated garage or basement or anywhere that will stay above freezing for the rest of the winter. You can remove the casing. Water them just enough to keep them going, about once a month.

https://www.gardeningknowhow.com/ornamental/foliage/japanese-blood-grass/care-of-japanese-blood-grass.htm

https://www.gardeningknowhow.com/garden-how-to/info/what-is-overwintering.htm

You can't go wrong with Miscanthus grass (maiden grass) and there are many varieties. They are a nice height for a privacy border. Zebra grass (Miscanthus sinensis 'Zebrinus') is attractive and tall. Miscanthus sinensis ‘Morning Light’ is another good one.

Here are some more suggestions:

https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-8/zone-8-ornamental-grasses.htm

If you search the internet for "living fences" you will see many examples and get some more ideas. Then make several sketches of possible layouts. For example, I saw some that were staggered, instead of a straight line.

You can also group them such as three junipers, then five grasses, etc. Or since the junipers will eventually be taller than the grasses, you could put all the junipers together starting in the middle, then stagger grasses in front of them. Whatever is left of the grasses could go on each end of the junipers. Lots of possibilities. Or starting in the center, line up junipers with a grass in between and whatever grasses are left could go on the sides or the front, depending on how long the property line is.

Here are some options:

https://www.gardeningknowhow.com/ornamental/foliage/feather-reed-grass/growing-karl-foerster-grass.htm

https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-6/zone-6-ornamental-grass.htm