undercoat advice

[5past6]

Any advice please, I have been tasked to paint exterior woodstained windows about ten years old not been touched since. I have rubbed down, fungal washed, hot washed with detergent and rinsed and applied one coat of zinsser cover stain, happy up till now.
The owner has purchased dulux weathershield dove slate satin as a top coat from homebase. Question is what is best undercoat between these 2 layers or is it only gloss in this non trade weathershield that needs undercoat !
Any help appreciated...

 

[HERTS P&D]

What does it say on the tin?

Andy

 

[5past6]

Hi Andy,
Thanks for reply we now have a change of plan in that the dulux centre has recommended using the trade opaque which they can tint to the same grey and do 2 coats using first coat as undercoat.
I have the choice of oilbased or the aqua range, thinking of the aqua then the remainder can be used on her fence but open to suggestions !