Have a goal of studying each language for at least 20-30 minutes every day. Spread your learning sessions throughout your day, so that you are fresh when you start learning Prioritize a language, For example, study mainly russian for a month. This means devote to russian double the time. With all that language learning make sure you don't forget to leave your house, socialize and exercise.

I don't think there's any magic and it does take a lot of time, but whenever you can link the things you learn together so that you help your learning of one language by learning another, you're getting a little bit ahead. For example, a good idea, I find, is to keep a list of the new things you learn, say new words. If you learn: das Hund in German, you can make a note with the English word "hound". So that you'll keep that in mind for whenever you see that word you'll know what it relates to. Then maybe you find things that will also remind you of a Russian word. Or maybe a grammar rule or sentence construction is similar in German as it is in Russian so that you'll remember that way... I think it's all about building your plurilingualism by building links :)