On paint, $23 should buy a gallon, Ace has a Royal interior exterior tintable primer for $22. We need the interior exterior stuff and tintable means they can color it, that’s good for our needs, although that’s a lot of burgundy inside and out. As it’s primer, we can cover it with different shades. I don’t know what the tinting costs, you’ll have to ask. We’ll still need exterior grade finish paint to go on top. Yea, they make primer/finish paint, but this is new wood, first coat, we want a primer to soak in and seal it up, rough cut, flat finish primer. Something we can add putty to, once we can see the flaws, sand a bit, make it right. Then put a finish coat on it, that other stuff is for already done once, this is first time. You might thin it a bit on the first coat, probably with water (latex), just a little so it soaks in, then another coat full strength a half hour later. If you like you can test it on a scrap piece, plenty of them. Find a coffee can to mix it down, another to clean your brush (on the back garage porch, rinse them first).
On brushes, I have a really cheap 2″ and several 1″ chip brushes (also cheap), looking on HD (better search engine than Ace) they have a decent 2 brush set for $8, an angled 2″ and a flat 3″ (you need a decent 3″ brush and a 2′ angle for trim work), looks pretty good, something like that. You have to wash them each time, and rap them on a post (left garage corner works) to loosen the paint, then wash and rap them again, 3 times minimum, then wrap them up in a paper towel a bit tighter on the bristle tips to keep their shape as they dry clean. A brush is a good tool, to be taken care of to make the good finish. I bought a bunch of paper towels today, use them.