i'm in your conscience
You can transfer gen III Pokemon to a gen IV game and then transfer it to gen V. When it's in gen V, it can learn moves from its gen V movepool, like Bug Buzz, so yes you can get it through leveling up. Or if you miss out on it by getting it too far ahead of the level it learns it, you can use a Heart Scale to learn it. The same applies to Charizard. Just remember, in order to transfer your Pokemon, they can't know an HM move, so you'll have to delete them if they know one.
Anyway, next time you have a question about transferring from one gen to another, ask in the General Q&A thread in Pokemon Gaming Central.