Be careful the products you use on the old finishes, may of them had shellac as the final top coat, and it is very vulnerable, no alcohol, saliva, or that type of cleaners. Use machine oil on a small corner it should loosen grime an restore the shine, be sure to wipe down with a very soft cloth afterwards. Be careful to not use any abrasives. Once you are done a good coat of turtle wax will do wonders.