RE: thinning down after bulking
There are a lot of strategies to avoiding entering a catabolic state while cutting. The most important is ensuring that the calories that you are consuming are clean, often (at least 6x a day), contain enough protein, and have a low GI. Also, water consumption and training hard are necessary as well. There are some suppliements and drugs that are anti-catabolic and can help in the effort (such as ECA).