Without stating the totally obvious it is always best to use surface coating products from one manufacturer rather than mix. Probably you had the Dulux etch primer left over from another project.
Assume you have used this? If not please advise what you have used.
www.dulux.com.au/specifier/products/466H0069
What Norglass coating are you planning to use? Assume a Northane 2 pack poly? Suggest call Norglass direct to confirm compatibility - their technical support is second to none and will set you right with no fuss. 02 9708 2200