First, let me inform you about big fish being off shore and on ledges; Big fish are shallow, deep, or somewhere between.
Seriously, big fish will use many different locations as their summer 'home.' Two things that must be present are the forage and security. Security for a bass can be depth, or easy escape to it, or cover.
As to pitching to brush in water 15ft-30ft deep, it is a much better option than casting. The most advantageous approach would be to pitch to the brush and strip line off the spool after it lands. This allows the bait to fall straight down, or as close to straight as you can get from a distance. Watching your line as it falls and keeping your rod tip up, engage the reel when the bait stops falling. Now jiggle the rod tip and if the bait begins to fall, strip more line. Repeat if needed. Once it's on the bottom, work it back up a short distance at a time. Your first bite will be an indication of the depth the fish are holding and you can then just target that depth as you continue to probe the brush.
This technique works best when flipping as you'll insure a straight drop and be pulling the fish up through the brush rather than pulling them out as your line can tangle on branches above the depth the fish.
IMO, the best time to target this type of brush is under post front conditions when fish are holding tight to cover.