Caulking shingle siding
We are priming and painting our old house (I posted a porch question also) and are total novices at it. I know that we are to caulk the gaps in the siding and shingles. My question is are we supposed to leave some areas open? The shingles I am working on right now are on a bit of a slope. Some of them are snug together and others have big gaps between. The bottoms of some are snug against the next row and others are not. Should we be caulking completely around every edge, even where they are snug?
Also, I see on the tube of caulk to use some type of backing under any gaps that are more than 1/2 inch. What do you use? They are irregular areas so small pieces of wood will not fill all of the area. I will try to get a picture up so you can maybe see what I am talking about.
Thanks for any advice!