I've never heard of "knotting solution" in the U.S. Kilz works pretty well, but I've had bleed-through after a period of time when using a light colored top coat. Several coats of Kilz might stop that. My father (a carpenter and cabinet maker), taught me to use shellac to cover knots prior to painting. That's definitely "old school", and there might be other products now... maybe polyurethane would be a good choice???