This advice is a little different to what I have followed in the past
I'm pretty sure Mike's advice is the best, he really is an expert, especially on re-sampling
Using Qimage means that your workflow can be very much simplified and the use of external programs eliminated.
Also,I am not sure how to save a 100% screen sharpened file in qimage.
If you look at my reply to your other post, you'll see that you don't have to, the USM filter is a separate file stored in the image folder.
It's the same with different print sizes, one image (the original size), does all.
Terry.