In regards to the rudder , Iv'e found that if you hold the rudder untill you see the plane turn then you probably have overcorected. I like to add  and then release the rudder stick in short blips. And not alot of rudder, just a little. As your ground speed increases you will be able to relax your control a little and plane will smooth out and go straighter.  It is really easy to over correct  and get squirly and/ or ground loop.