I think it looks like magnolias. Here's a youtube tutorial if you like. You don't have to have special cutters for them, I have used my rose cutters and they came out great.
There are a couple of recipes at this link http://ca.answers.yahoo.com/question/index?qid=20080304213419AA95yzN
I personally would not use shellac on cookies even though it is used on gumpaste art, it doesn't even wash off brushes.
LizzieAylett is right, if you put the buttercream in the bowl and as long as the beater is totally immersed in the cream it will whip smooth and no bubbles. I also read somewhere that if run the cream in a food processor it will smoothen out but i have not tested out this theory.
Cherimoya, yumm I loooove them, the last time I visited my mum I ate so many but I didn't know the seed was poisonous.She has so many trees, that almost every day there was more than basketfuls picked until the end of season.sorry getting side tracked here, down memory lane.
I think the metal for soda cans are a little too thin ( cake might burn) and I am not sure on how the paint on the outside will be when placed in a hot oven. I would empty out some canned corn or other vegetable, peel off the labels give it a good wash and use those can as long as it is not painted inside or out.