Just order regular strength at first, until you know which products work best for you, and how much you personally need of each for the best effects, since its different for everyone.
The consumer products and Instant line can be used on their own, or in any combinations. It is highly recommended that you test each product out on its own before combining, so that you are comfortable and familiar with the effects of each and the amount you need of each. This post might help How To Find Your Sweet Spot (How to find your sweet spot...).
This way you don’t waste your products, and you don’t waste time either. Some people recommend that you purposely OD on each thing, just so you know how it is, but thats up to you.
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You can do both, you can put Instant Shine (or any other product) just about anywhere you want. Some say the back of the neck is a good application point too.