As far as brushes go, the cheap way out is a boar. But like what was said, it takes time to break in. Another option 8s a synthetic brush. They are normally very soft and dont have a lot of backbone but if you put your finger over the handle and the tips on the brush knot you can get a little more stiffness while loading your brush.
Low cost badge brushes ive found have a tendancy to shed. So thats another option but you might be picking hairs out of your soaps. Burushes are a personnal thing. Ive got some low cost brushes that i enjoy and ive got exspensive brushes to that i like. You just have to see what you enjoy the most.