Unless you prefer rote learning as a learning method, I (personally) don't believe copying characters does much to help learn them at all. It might help you remember a large amount of information for a short amount of time (i.e. cramming for vocabulary tests or something) but it does very little to help you actually utilise them in the long term.
I think a better way to learn would be to write them into sentences - or, even better, use them actively in practice essays. The more times you write them in context, the more likely you are going to remember the characters as well as their meanings.
With idioms, there's nothing wrong with using a notebook to write them at first, because you will gradually come to remember the more useful ones. Seriously, some of the phrases in the XJS list are utterly and completely useless, in addition to being tediously long and difficult to write and remember. And plus, your grasp on the actual language is far, far more important than how many idioms you can regurgitate.
With types of essays, I found writing persuasive and evaluative essays the easiest since they're quite similar in style and content, and like strawberries said, they have an almost fail-proof 'formula' to adhere to. They also have standard idioms you can use in most pieces. Personal and informative pieces rely somewhat on improvisation, and I wrote zero imaginative pieces through the whole year because I'm a depressingly uncreative person. Though you need at least a basic grasp on all/most essay types, I think the most important thing is to find what style
you are most comfortable with writing, since it's different for everybody.
So that's my two cents. I'm really sorry if I come across as stuck-up and condescending... I don't mean to ><;;