I haven't personally used the bleach spray, because I don't spray anything on my plants - advantage of greenhouse is keeping the leaves dry. But I can certainly vouch for the worth of bleach against grey mold - the only way to keep pruning cuts from becoming a source of infection or re-infection is to dip the pruners in bleach. This has made a huge difference for me when I wanted to keep a plant going even though a main stem had to be taken out.
