Those darn sunken in areas

If areas are sinking consistently, that means you didn't use enough medium in those places. You may use a retouch varnish, after the fact. Since retouch varnishes usually contain Damar, some prefer to mix up their own oiling-out medium instead. Take your normal media, in my case, 1 part Stand Oil/ 2 1/2 parts turp. Mix up a media twice as lean, 1S/5T. Use that to oil her out. The faded colors should instantly come right out.
Wait at least a year before applying final varnish. I've been led to believe that another layer of paint ought not be put over the final varnish.

[Peggy Baumgaertner]

I spray with retouch varnish, but the only one on the market that still "works" is Blair. You need to do some research on Blair, because I hear they are discontinuing it. Jerry's had it the last I looked. Steven is right, you really should not be painting over a varnished painting. If you find you must repaint (......when I get that feeling, I go lie down until the feeling goes away....), the varnish needs to be completely removed before new paint can be applied. At that point, you are getting into a major archival area, and can seriously mess up your painting. Better to wait two or three years to varnish, so you know there will be no corrections. I spray with retouch varnish (Blair) before the painting goes out.

If I find I need to make a correction after I've varnished, I remove the old varnish (it takes hours, cotton swabs, clean cotton cloth, turp, and tremendous patience), apply the paint, and spray with retouch varnish....and pray....

You cannot varnish twice.

[Mark Branscum]

Originally Posted by Albert Loewy

If areas are sinking consistently, that means you didn't use enough medium in those places. You may use a retouch varnish, after the fact. Since retouch varnishes usually contain Damar, some prefer to mix up their own oiling-out medium instead. Take your normal media, in my case, 1 part Stand Oil/ 2 1/2 parts turp. Mix up a media twice as lean, 1S/5T. Use that to oil her out. The faded colors should instantly come right out.
Wait at least a year before applying final varnish. I've been led to believe that another layer of paint ought not be put over the final varnish.

Wait a year for a final varnish ..... Do you work this out with your client to get the painting back for final varnish? What is your process here if you dont mind me asking?