I had a closet that needed to be closed up, and I was new to drywall. I ended up using way too much compound, but was able to sand most of it so that it's smooth the touch and belnds pretty well with the rest of the walls. However, even after priming, you can still clearly see the 1 foot wide area that I put compound on. What can I do at this point to fix it before I paint the final coat? If I sand anymore, I think I'll be hitting the joint tape.