/sci/ - Science & Math

What's the best method of studying multiple subjects? Like say I want to learn japanese, drawing, and writing a good essay.
Do I study each one 1 hour a day for 3 hours a day?

Or do I study one subject 3 hours a day and switch subjects every day?

And finally, when studying, is the best method 20 minute sessions of pure study and 5 minutes rest in between each set the best for memory retention?
or is there a better method?