GH isn't going to give you the same kind of results you'll get from AAS. The effect is much less dramatic and takes long term use to get the best effect. The best time to add it in, is before a show, when getting lean is your prime goal. I would run it for at least 20 wks, leading into the show. For this purpose, 3-4iu ED would be enough to get a solid result. 

No matter what, GH is a long term plan. So after the show, it would ideal to stay on and continue through your off season, and see how you respond. It can lower your response to insulin at higher doses, which is ideal for fat loss when dieting, but that can also be less than great for mass gaining phases. This is why guys often combine GH with insulin in the off season, Insulin use is a while other conversation