Keep at it. You'll find some coins. My 1855 seated quarter, 1858 silver 3 cent piece, 1835 bust dime, and 1891 seated dime all came from the woods in the middle of no where. And like you I was digging a lot of shot gun shells in those areas. I also have pulled a barber half, a walking half, and several barber, merc, and rosie dimes, along with a barber quarter in the woods. Then there's the V-nickes and buffalos and large cents. The number of coins you find may be slim but the quality of them is usually very good. Sometimes you'll go for hours without a good signal. I usually don't dig the shot gun signals anymore unless I feel like it and am hoping for a gold coin or ring or something.
What I do is look at the layout of the woods. I try to hunt ridge tops as they were often used as highways on both foot or horseback back in the day. Hunters also favored walking the ridge tops too because they could spy game from a distance. I also look for bottlenecks...Places where there is only one way up or down a ridge. Can't tell you how many good coins I've found on the slopes going up or down a ridge that were the only way to cross them. Always good spots. Around water is good too as they often camped by water sources. Even a small creek.
You soon develop an eye for what areas are dead zones and what ones are potential traffic or activity areas. I pay attention to the threshold and if it starts nulling out, indicating iron, then I know I'm in an area where humans have done things before. Keeping an eye out for pottery shards, bricks, old trails, non-native plants, etc...all of these things can indicate old house sites or places of activity.
Woods hunting is my favorite. On a hot summer day I can stay in the shade under the trees and out of the sun. You don't have people looking over your shoulder and no worries about getting kicked out by the cops or something. I usually hunt areas with older trees where there isn't much ground cover. The areas with ground cover I hit in the winter when it dies down.