What is the best way to cut a branch to size but also promote new buds at the end. And im curious if i cut a twig off will another grow back in that spot or very close?

Arigatou gozaimasu, Mr. Miyagi

That depends on a lot of different things. How old is the tree, how big is the branch,What is the over all health of the tree....
Can you post a picture?
Where are you located first of all.

Im in Southern California. The tree is 5-6 years old. The branch in question is 1/16-1/8 in. I dont want it to get any bigger. The tree is in good health. If I remove most twigs from a branch, to provide better sunlight to lower branches, I would like the fullness of twigs to return.

When the tree is actively growing pinch the needles on the tips of the branches. That will promote back budding.
You need to take into consideration that cutting junipers will cause the foliage close to the wound to brown....especially on branches that small.

In general, if you cut of (part of) a branch, all of that branch will die back to the point of closest foliage. Removing a branch will NOT necessarily lead to new buds. So tread carefully.

You've a lot of options to keep the size aspect with the remainder of the tree.
As stated before me, pinching will cause back budding, particularly if vigorously
growing.

I would thin the branch, removing alternate secondary branches of less promise
than the alternate one (plan your final look 1st) then do likewise on tertiary branches
and wire to plan, then pinch back remaining foliage after a couple weeks of recovery
allowing weeker branches elsewheres on the tree to grow out with only minor corrections
if any at all. Now you're forcing growth elsewheres. The branch will in time grow, but
this will keep the aspect ratio with the tree.
The thinned branch will fill back out and need perpetual thinning with good
feeding till Fall. Then follow with 0-0-10 fert to harden off the new growth as the
Nitrogen and Phosphorous is removed from the diet. Just remember to continue
your program next Spring to keep the growth in check.

all said pics would help tremendously. A 5 to 6 year old juniper could be alot of shapes and sizes