You don't say how tall you intend them to be allowed to grow, but with the possibility of 15 feet ultimate height, I would not be thinking of pruning at all for some time. Al

Shear lightly very several times a year beginning now. Just 1 or 2 inches at a go. Think light and frequent. Keep an eye on them and when you see several inches of new growth, take off just a bit of it. You want to increase tips to achieve density and it is light tip shearing that does it--it increases branching and density. They do most of their growth in the spring but a little in fall and winter also. Summer they don't do much. Do not worry about leaders, there will be multiple leaders.

Look at the first two photos on this blog post. They are both photos of
'Silver Sheen'. The first is untouched, the second is what regular
shearing does.

look at first two photos, both of 'Silver Sheen'

hoovb: I'd like to see that post if it's still available . Mine reached probably over 15' in less than 2 yrs from 5 gal containers in zone: Salinas CA, Monterey County. ( I think it's zone 9 or something, there's no clear map on line as it turns out or info otherwise, unless sub-business card size zone maps are what everyone else is using, and they're all blurry at that - I long for the days of the Sunset Western Garden book, no problem learning my growing zone there. )

Anyway, they were supposed to do "up to 3'/yr" so since they stated out 30" to the tips, I thought in 3 yrs my neighbor's yard would have privacy from my second floor windows. Instead they got to over 12 feet in one year

this is the only photo I can find, Dec 5, I'd planted them Mar. 7

Point is: Now I need to prune, they're encumbering the paths.

It's not as complicated as you think. Follow the advice above and don't overwater.

iamericaru2

What was the right solution here? Would like to know for my experience. Thanks!