Here's a helpful tip I recently discovered while wanting to click + drag from my Desktop to an overlapping window.
I had just cleared my windows with the five finger "spread" gesture, but wanted to go back to my Finder window while still holding onto the file. I instinctively tried to do the five finger "pinch" gesture without lifting my clicking finger, and sure enough, it worked.
It takes some getting used to, but it works great. Try it by clicking and holding a file, then completing the "pinch" or "spread" gesture with the rest of your fingers. Your clicking finger doesn't even need to be a part of the action.