Trouble with unwanted hardline edges (overlaps)

With Anna's method, accidentally getting hardline edges (where your patches of painting overlap each other and create darker lines) is usually not a problem at all. So don't worry about them! As you'll likely be applying a layer on top of the one you're working on, the new layer will make the hard lines much less noticeable, without you needing to do anything specifically. 

Also, the lines can actually be a good thing and used to your advantage. In all except the smoothest of visual textures, there will be some sort of texture to create with your brush strokes which is why Anna so often uses a stippling type brush technique. If you make sure that you apply the paint in the direction of form (Anna always shows you how to do this in each tutorial) then the overlaps can actually work to help create your subject's form.

See the Brush Techniques Knowledge Base video for more information on this and demos.