A couple years ago I did several variations of a Heather Ale. It was all done with dried heather tips because I don't know anywhere nearby where I can get fresh heather. The batch I liked the most had 4 oz of heather tips added at 60, 30, and 5 minutes. And then I "dry-herbed" with another 4 oz for 2 weeks. This ale really had a forward heather tea flavor, which was what I was going for.
I also did a series of meads with heather tips. For one of them I steeped the tips and then used the tea to make the mead. And for another batch I added them to the room temperature mead after fermentation was done. The one with the steeped heather tips was much better in my opinion. It had much more complexity.
I think a hot water method (whether it's a boil or just steeping a tea for a later addition) is the best way to go. When adding to your boil, definitely use a bag of some kind to keep them from getting everywhere. If I brewed the ale again I would probably drop the dry-herbing because it's such a mess.
In more recent days I did another Heather Ale. It didn't come out well because of things unrelated to the heather, but I tried another method you could consider. Once fermentation was done, I racked off 1/2 gallon of the beer and heated it to 160 degrees. Then I steeped 2 oz of heather tips for about 12 minutes. Then cooled the beer back down and added it back to the batch. This is a method I would like to try again at some point.
I haven't used Juniper so unfortunately I can't help you there.