Hi Just 10 here are some tips that will help you for next time......Iif your getting a built up edge then your paint cote may have been applied to thickly.Are you using an airbrush or aerosol can ? different factors can cause this suchas the airbrush being to close or to far away from the subject.......or the airbrush is not moving across the subject in a gentle sweeping uniform motion.Build up light coats gradually ! Make sure your mask is sealed properly before you paint ( tamiya masking tape is the best !)
Always spray light coloured paints such as yellow before darker colours. Weak pigment colours such as yellow and white will often need a light undercoat .( testors aluminium plate buffing metalizer is good primer for this.)
To sand back paint you can use wet and dry sand paper (use it with a little water )which can be found at hardware stores working from around 800 grit or so (Depending how thick you layed it on)through to 2000 grit . this will work out the scratches.
hope this helps ...........Peter.