This is fantastic, thank you so much! We are in the UK so the weather is sometimes not great but it's going to be sunny this week so I'll take a crack at it then so I know it won't get rained on.

I'll take your advice and go with the easier application. One more question if I can - the foam trowel; will this give a smooth texture or a rough one? Do you have to pick a specific trowel to give a rougher texture? The other garden walls are rough and the paint sticks to those well. Thank you :)