The simplest method to accomplish this is by color/pen relationship. Take the colors that represent the items to be 'ghosted' and in you pen settings, assign them a grayscale - say 50%. The other items will plot with their full 100% density and will appear bolder. If you wish, you can also assign different(heavier) plot weights for the items that you want to accentuate.
Using this scenario will require that you use discrete colors for each set of data - ghosted and bold (normal). The easiest way to do this is to assign the 50% grayscale to a range of numbers that you seldom use - say 240-255. Then assign the appropriate colors to the layers containing the entities. If you use Layer Manager to save the original settings, and the new settings, you can switch back and forth by restoring layer states.
You can also accomplish this by using two sets of pen assignments and leave the layer colors alone. I would save both to separate pc2 files so you can plot normally and accentuated simply by using different pen assignments. For this to work consistently, it is important that you are consistent is layer color assignment across all drawings.
