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Staining is difficult for water based paints to control. I use Cover Stain from Zinsser which is oil based and drys very fast (but is not micro vapour permeable, damn) Having read the tin for Zinsser 123 I note it says that you need to allow a much longer than normal drying time to improve the stain blocking. In my experience it doesn't stain block but I've not left it to find out if that improves with time.
tldr Use Zinsser Cover Stain for guaranteed results.
I’m getting staining through two coats on ten year old pickets, which I never had with the Superdec. I have a tin of Zinnser primer somewhere, so I’ll see how far that will go on the rest. I picked up the recco for the Barn Paint from Painters Pit Stop.