Frequently, until well rooted out. Need will vary with weather conditions and soil textures involved. Put on enough to moisten entire root mass. It's not like checking the oil in a car, where there is a standard method that works for them all everywhere. You have to learn how to judge the situation on your own. If completely new to this maybe take a similarly sized potted plant that is looking dry on top of the potting medium or starting to feel comparatively light (both common indicators of a likely need for watering) and see how much water it takes to remoisten the entire soil column in the pot. This will give you a general feel for what is involved, anyway.

Once you figure out how much water they need, and how often, the most efficient method would be a drip irrigation system, with 1-2 emitters for each plant. The number of emitters is based on how much time you want to leave the system on to provide the appropriate amount of water. This delivers water to the shrubs only, with minimal evaporation. You can buy kits and parts at Lowes or HD, and install it easily.

Soaker hoses work very well, but aren't as discriminating with the water delivery. They work just fine in densely planted beds and along rows of veggies and such. All my nursery beds have buried soaker hoses, approximately 4" below the surface. Costco frequently has specials on them, and I stock up. This year, I'm going to bite the bullet, and buy a bulk coil or 2, with the fittings, and make my own.