My husband had an Aunt who did decorative pieces that she painted - she was a master at it. Most were pieces that her husband cut for her on the scroll saw (and where I got my first introduction to the scroll saw oh so many years ago now.) Most would refer to the type of painting she did as "decorative painting" or "tole painting." While "tole painting" is using lots of decorative strokes, the work they do at first to prepare the wood for painting is the same we would all want to follow even for doing simple painting of wooden pieces. Because of her and her beautiful work, I took some painting classes many, many years ago. One of the first things they teach you is that it is usually best to seal your wood before applying acrylic paints. After applying the sealer, check to see if you have raised the wood grain and if so, do a light sanding. Also, as already noted by others, you do not want to overload your brush, nor put too much paint on as your base coat. Too much paint and it will not dry smoothly.
There are several places you can find information on the basics of tole painting. Sheila Landry, who sells a lot of scroll saw patterns used by many, also has a painting site. She has Youtube videos she has done on decorative painting. I took a quick glance there and didn't see any real "basic" information though. Decoart paint, is one of the acrylic paints used by many decorative painters. They have some good basic information on their site that can be found here: Videos and other info.: https://decoart.com/comepaintwithus/ - mainly look at the information they share in regards to base coating unless you want to learn more about decorative strokes. Then they have a PDF you can download over on the right side of that page called "Come Paint with Us An Introduction" that can be found here: https://decoart.com/comepaintwithus/DecoArt_Come_Paint_With_Us.pdf . Page 3 provides the basics in regard to brush care, sealing, and base coating. Here is what it says in regards to "base coating":
"Basecoating is the application of smooth coats of paint done with long brush strokes to create opaque, complete coverage. Use the foam brush included in your kit to apply one to two thin coats. Wash the brush immediately and set aside to dry.
When basecoating, use the largest brush available to t the design area. As the paint dries, it feels cool to the touch. When it returns to room temperature, you can proceed."