This is all new to me. However, I did go to the store(s) yesterday and told them what I wanted to do and asked what stuff was available. I looked at the tubes of caulk and none of them mentioned use for filling gaps, sanding, and painting. The salesperson thought the caulk they had would not work. I don't know about painter's caulk specifically, but I do have tubes of window and door caulk that I will use around the trim boards after I get everything painted. They did point to the canned wood filler putty, but that was pretty expensive.
Anyways, it was my impression that the caulk was made to stay somewhat flexible and could not be sanded. Whereas the DIY sawdust and glue putty I mixed up will harden and should sand down nicely, and then paint over it.
I did not compare the price of caulking to the cost of my DIY putty mix because I was lead to believe that the caulking would not work the way I wanted it to. I could be wrong, and I certainly don't think the salespersons I talked to had any real-life experience with any of the products they sell.
Someone here on the forum mentioned about using glue and sawdust as a DIY putty, so that is what I am trying. Also, I watched a number of YouTube videos on using the glue and sawdust mix for my application and I think it will work.
If there is a caulking that would work for my application, I would love to use that as I already have a Ryobi 18v power caulking gun and look for excuses to use it. I'm all for using off the shelf solutions that are cost comparable to my DIY solutions. Using a caulking gun would be faster and easier for me. But my DIY sawdust and glue putty mix was pretty easy as well.
View attachment 3595131