Sorry.. I'm only familer with Photoshop.. I've been using Photoshop for a few years now and am totally addicted to it.. Trouble is the program is so huge with my memory I'll never learn it all..But that might be a good thing because I'm always finding some cool new way of doing things.. I'll tell you what I discovered in Photoshop and maybe somehow it will help you.
First put two photos of the same size together each on there own layer.. Then go layer/add layer mask/reveal all..
Then use gradient tool/foreground to transparent on the top layer... Yes.. Very easy to use,but you stiil have to play around with it to get the desired effect.. Everybody else probably knows this already, but I sure didn't... :)