Well I disagree, Firestone may say you need to coat both substrate and rubber but with wba it will make no difference if you wet lay the covering. If fact many of the other suppliers of epdm wba state you only need to coat the timber deck.Nope! Both the rubber and the wood must be glued together. I'd dig out the Firestone factsheets but it's past my bedtime.
https://static.rubber4roofs.co.uk/s...chfiles/w/a/water_based_deck_adhesive_tds.pdf
This adhesive is designed to be roller applied and used as a one sided, wet lay in adhesive on flat roof decking surfaces.