You need to sand out all the big defects first if you want good result. From past experience even using chalk paint it is better to use a primer. Unsealed wood can still bleed through the paint. No worth the risk in my opinion.
I agree. A primer is needed, maybe even shellac if there are knots in the wood.
Here is a great tutorial on how to paint furniture. Definitely prime for bleed through with a pine dresser though! https://www.arayofsunlight.com/how-to-paint-furniture/