re: Make my own flower paste/gumpaste or buy ready made white and colour myself?

I tend to use commercial bought flower paste if I want more realistic, delicate flowers, Platinum paste is superb. For the stylised flowers, which I tend to do a lot of, I add cmc to sugarpaste. As above, dusting flowers is great fun, you can really add subtle detail. I also have a portable steamer to help set the colours and give a bit of sheen (very cheap on eBay).