How fun that you got to do an over-sized version...it's great! And (to show how little I know about painting) I found it surprising that the background comes first!
Well, that's just the way I do it (when I'm using a knife). I have no idea what the "proper" way to do it might be... It didn't take many knife paintings to discover that: - knives are not enormously good at precision, so butting up to another area is difficult - backgrounds look quite good done loosely, which means even less precision! - oil and acrylic are both mostly opaque (the yellow in this painting is not entirely so), so you can cover up the loose background without too much trouble - the impasto effect is more effective if you work from back to frontPencils are much better precision instruments, as I know that you know!
Tell me what you think!