Best method to ensure scratch coat (render) adheres to brickwork
In the UK, in situations where you might be slightly concerned about the surface being rendered, a coat of equal parts water &amp; UniBond PVA Adhesive &amp; Sealer is applied to the surface prior to the scratch-coat going on.

If the brickwork is quite porous, wetting it down beforehand (just prior to applying the UniBond PVA Adhesive &amp; Sealer) with a hose wouldn't be the worst idea, also wetting down the scratch coat before the top coat is applied isn't a bad idea (especially if the weather is on the warm side).

Adding a plasticizer and waterproofing agent to the scratch coat is worthwhile (normally specified, required).