I use opaque water based ink and I want to know what emulsion dip should I get.

I would recommend Saati graphic HU for water based.

http://catspitscreenprintsupply.com/saa ... on-gallon/

Hu will work for short runs. We would recommend however to post expose the emulsion for medium length runs (2-300 pcs). If you are doing extremely long runs we would recommend DW.