Best thing to deal with shadow is a colour correction palette or if you don't have that some orange lipstick blended well will do the trick. I don't have a beard shadow anymore but I do have dark spots. Depending on what I am trying to correct will depend on which colour I use. When I did have a beard shadow I would use orange corrector to hide it. When you are putting your foundation over the top use an applicator as it will go on much better and far more even, don't forget about your neck.
Colour correction palettes are not expensive. You do not have to buy expensive cosmetics some of the cheaper brands are better. I have a $60 mac foundation that I rarely use as I use a target brand long wear full coverage foundation which I think is $8 a bottle and I get complimented on how natural my makeup looks. Good luck and I hope you can fix your shadow issue to your liking.
Take care
Liz
