Yeah, the spraycan thing is seriously ridiculous. Why not wish for a bazooka or a chainsaw ?
...or just wish the monsters themselves were gone.
Personally, I'd just wish I had the powers of Superman.
BTW, on another note, the first film is basically the first half of the book by Michael Ende, and the second movie is essentially the second half. The first film is much closer to the book.
But, I might add the whole bit where he loses his memory is not caused by the evil queen type lady in the book. Rather, it's simply a side effect of the wish itself. Like, the kid in the book is fat and short. So he wishes to be tall and handsome - but then loses the memories related to ever not being tall and handsome.
It's a much better way of doing it, and really is a much more effective story device.