Careful using WD-40. First, it's a spray and will get all over everything. If you must spray it on a rag and work with that. Second, WD-40 has lubricants in it that will stick to the frame and attract dirt and grit. If you use it make sure you chase it with something like mineral spirits to get the residual off. Third, if you have to use mineral spirits to remove the residual, you might as well start with mineral spirits and see if it works.

Go simple first, then use more agressive measures if necessary.