You could try Zinsser BIN. Shellac based, and it's white so acts as a primer and undercoat. You can use it to "spot" the knots, but might be best to coat the whole door with it. Work quickly tho, as it dries super fast !
Sadly Amazon don't deliver a lot of products here. Screwfix have started delivering to Slovenia but very limited range. I have found one firm on eBay now who will ship to Slovenia but not cheap. Think I'll have to bite the bullet though. I guess due to the possible flammable qualities shipping is dearer than normal.
Y Yes, Zinsser BIN looks ideal. Have found a firm on EBay who look like they will ship here, not cheap but might not have any choice.
you can get the shellac though it's just the meths you need now. According to wiki meths is just ethanol with additives to stop you drinking it. You must be able to get ethanol out there.
You can get it over here at numerous outlets. Screwfix don't sell it but you can get it from Tradepoint at a reasonable price.
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