Lazy lightning,
I think that yukishiro said something very important which I'd DON'T fertilize too heavily. IMO miracle gro every week is too much. Do half strength or a little less if you fert every week. I would use some organic fert which will give tree vigor without excessive growth. Get it healthy and trim back once per yer in late summer.
Yours needs to get vigorous, it doesn't pay to work juniper too hard, just slows down the training process. Someone said, was it grimmy, that the slow way is the fastest way to train bonsai, ESP true with conifers.
You can get shimpaku or procumbens mail order from Meehans miniatures in Maryland . Good folks to deal with. Spend a hundred and get something nice