DO NOT use nail cleaner on your bird. It's highly toxic! You will kill your bird.
If the area is badly damaged, use a cloth soaked in warm water and Epsom salt and clean the wound as best as you can.
You said your vet already looked at the bird. Many vets are not trained in avian medicine. You may wish to consider getting another opinion. If your vet did not do a CDC (complete blood count) looking for liver desease, you may want to consider it. Before treating feather problems you must first eliminate health problems. Liver desease is a common cause for plucking.
If your finances are tight do the following:
I give severe bird pluckers a few drops of wheat germ oil until the cause can be determined.
Birds pluck because they are stressed or out of boredom. Did you move recently? Did his environment change? New cage or location?
Get him some toys to play with. Quackers loveto weave. We recommend getting Quackers some long leather shoelaces, ty-wraps, straw, or anything that can be woven in the bars. Give him something to do!