How to know when window has completely painted?

I have a window that needs to run a length process. The process is threaded so it doesn't lock up the screen. However, I need this to run when the window is first loaded, not based on a button click or anything. The problem it creates is that it causes the window to stall a bit when initially painting itself. I even tried to put the call to the method in the Shown event, although it helps, it's still not perfect.

Isn't there a way to absolutely wait until the window has completely painted itself? I think it would make for a much more polished look. Any help on this would be appreciated.

Try calling the form's Refresh method in the Shown event handler, then start your other thread.