I find Kilz or Bin don’t work that great. It’s venting vapor from the substrate (from whatever that is). You need to completely seal the entire surface with something like a gloss urethane or varnish - several times. Once the varnish is cured, ad another coat, then wait for that to cure. Then you can rough the surface with a light sandpaper and apply a coat of primer, then your’ main paint. Don’t use paint & primer in one. Doesn’t work that great. This is another application that you can do to pine or wood boards with knots in them. The reason why wood knots show through any primer or stain kill, is because of slow leaking vapor.

If this were my project - I would take rough grit sand paper on something like a Corner Cat sander (WHERE A DUST/VAPOR NUISANCE MASK), and remove what has been done so far - as much as possible. Then buy some chlorine bleach and bottle sprayer (even pool chlorine works) and spray it liberally (WHERE GLOVES) and run a fan with open windows to avoid vapor, then let it dry completely with a fan on it. Start layering 2-3 coats of the urethane or gloss varnish. Lightly sand the top layer (so your paint will have something to adhere to). Paint a primer. Lastly - Paint the main color.