How do I water wood to open the grain?
I prefer to use dyes first.  Metallic dyes can be mixed with either alcohol or water.  Using water will raise the grain, alcohol won't.  Dyes allow a progressive tinting, that is even reversible.  Dyes penetrate more deeply, compared to pigment based stains.  Dyes can also tint shellac as a base coat and will seal the wood for any further finishes.

The grain will raise slightly with the first water coat.  Light sanding with 220 will knock it smooth. Be sure to use an dewaxed shellac as a sealer. A 1lb cut is sufficient for sealing.

Once the color is sealed, water based finishes are fast and a lot easier to get a dust free finish, compared to an oil poly.