if it were me. ...

i would plant the shrubs ... and kill the grass with roundup .. as the shrubs take hold and expand .. [no need to do it all this season.. as it is holding soil] ...otherwise.. in 5 years .. you will have grass growing thru the shrubs.. and it will be an ugly mess ...

as you note.. hand picking grass IS NOT GOING TO WORK ... ever ...

planting into the side of a hill is tricky.. i think it is covered at the link ..

ken

Here is a link that might be useful: link

Based on my experience, I'd not kill the grass. We have fine sandy loam soil and a steep bank (an old river terrace) which we killed the grass on when I planted shrubs. We mulched well. The soil has definitely slumped some - the shrub roots don't seem to be as deep or as tough and binding as the roots of the grass that was there before. We ended up pounding in stakes to use as soil pins and they seem to have helped. Leaving the grass would have been less work. I think if I were to do it again, I'd heavily mulch the area around the shrub to reduce competition and then hope that mowing with a weed whacker as needed would be enough to deep the grass under control.

If you have different soil, you might find you have different results.