Stencil tips for reballing/bga rework

Couple questions:

1) how do you guys make the stencil adhere to the ic you are reballing? The most frustrating thing in the world is when solder paste gets under the stencil

2) what is a good way to measure the solder paste quantity needed? It is just a dab or do I need to fill the apertures all the way up?

Any other tips and tricks are welcome and appreciated, thanks to all replies in advance.

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