But you won't get field experience if you're not able to ID a bird. In order to gain experience, you have to be able to separate the easiest species and you must know the features to separate the birds. I won't gain experience in identifying pipits if I cannot separate them from the Skylark first.
I always prefer to have at least one feature, that helps you to separate apparently non-confusable species.
And actually, to be honest, I haven't seen many birds out in the field, but I look at them in the guide books or on the Internet so when I see these birds in the field for the first time, I know which species is that, even though I haven't seen it before. The same goes with the birds' songs. Initially, I listen to the songs/calls at home, and then, when I hear such a call in the field, I know what it is.