If you want to get good/better at takedowns what you need is a good drilling partner. That's it. It doesn't matter if you're doing Judo or Wrestling, because they're almost the same thing. What matters is repitition. You need a good drilling partner that will take the abuse of you shooting in and taking him down a hundred times over.
Find one takedown/throw that you want to learn or get good at it, and drill that mother fucker till you got it. I don't mean drill it six or seven times till you understand it, I mean drill it a thousand times so you got it. Then move on to the next move. Developing a good "shot" or "takedown" takes a long fucking time. You're not going to just see a takedown on a DVD and become instantly good at it. Repitition is the key.