How can I insure my privet hedge grow contained by gluey? They are just starting off, planted them as twigs 2 months ago....

They are just starting off, planted them as twigs 2 months ago. (They are give or take a few 3-4 foot high now). Right now, I hold only trimmed off the small twigs that did not enjoy any growth coming from them. Should I cut back the growth that is extending out so that it doubles up? (Right in a minute, that growth is about a foot long on most of the hedges). Am I right? > Whatever I cut, will it grow back doubled?
Answers:    "Am I right? > Whatever I cut, will it grow wager on doubled?"

Yes, sort of..
Any time you cut off the end of an actively growing branch you own removed what is called the "terminal bud", this is the bud that makes the branch bring back longer.

By doing so, you activate dormant "lateral buds" along the branch. It is possible that one bud may grow, or many may grow into foreign branches, "thickening" the shrub. I think this is what you are think of when you said "will it double-up".

So dance ahead and trim away some of the new growth. The buds may form at the base of any fern that you leave, and will usually form close to the cut.

In the future, as the dissemble develops, be careful not to "shear" the plant, that is to cut away adjectives of the new outside growth, or you will end up beside too many small side branches and all of the foliage will be on the outstandingly outside of the plant with a bare center. - This is easier said than done to explain, but I'm sure you've seen old shrubs and hedge with a bare center. That's cause by to many years of shearing.
yup! cut it back...it'll sprout out and procure bushier each time you do that.