Opinions differ on the subject of adhesives. Some want the strongest adhesive to achieve maximum strength and rigidity. However, this strength and rigidity is an illusion. Even if I glue 10 mm thick angles to the sandwich panel with the strongest adhesive in the world, the weak point is always the connection between the panel and the polyurethane foam. These bonds simply separate if the applied force becomes too great.
In the automotive industry and specialized workshops, MS polymer is now almost exclusively used. Besides priming, sanding may also be necessary. Fortunately, professional applicators know what to use, when, where, and how. Read the data sheets and, if needed, seek advice from a specialist retailer or the manufacturer. (A DIY store is not a specialist retailer.)