planting bare root hedge

That's the advised way to do it, Jbt.

A great deal depends on where you are planting, Dig a ditch by all means , but individual holes for the trees will suffice, but do make them big enough to ensure plenty of root room, in which case a trench is probably the easiest thing to do . Those are both tough trees so should make you a good hedge.

I did quite a lot of tree-planting when i volunteered for teh Nature Trust - because we had loads to do and limited resources, we had these special long, narrow spades and just stuck them in the ground, opened up a hole, dropped the young tree in, pulled out the spade and heeled them in. Effective and prob easier than digging a trench - sounds backbreaking...