I can't think of anything that will keep the hair straight, both of my dogs are the same way. I can bathe them and they look awsome, two days later they start to get curly again it doesn't help that Florida is a high humidity kind of place most of the year
As for not picking up half the forest I am not aware of anything that will stop that either, however there are products that you can use to make it a snap to get the forest out of the coat. The one I'm using now is Ice on Ice. I spritz to area and brush through it helps me keep my younger spoo mat free as well. Glow coat would probably also work, you can order that in petedge. Makes the hair really silky but doesn't really soften the coat like a conditioner would. It's advertised to repell things like dust and dirt and urine. I dunno that it really does to be honest but I like it anyway.