I tried the same thing years ago and could not get them to look good after years of pruning. boy, do they get big! I evenutally got rid of them. There may be a right way to keep them pruned to stay in bounds, but they are probably best in a location where they can sprawl and keep their natural shape.

my best advice ... being a person who doesn't want to work that hard every year ...

prune at or about ground level with a chainsaw dig them out and be done with them ... juniper will die if cut at ground level ... no dormant buds to resprout ... or if you favor digging out the roots/stump .. leave a piece of trunk to help with the process ....

they are the wrong bush for the wrong place ..... at the wrong time if i happened to walk by with the saw .. lol ...

do some research and find plant material that is better suited to its location ...

and dream of all those hours of leisure previously wasted on them ...

good luck
ken