First tried to edit Tsubaki's idle standing animation, then tried Lambda's idle standing animation.
For Tsubaki I was using that thing that appears to be a piece of her hat at the top right. For Lambda, the little yellow dot to the left of her. I made sure everything was lined up pixel perfect.
I didn't resize the sprites, but I did copy-paste them to a uniformly sized canvas (seeing as they were all different resolutions, for some reason).
I tried first with Photoshop CS4 and then downloaded GIMP after I gave up on thatm but GIMP confused the fuck out of me and I didn't even make an effort to start editing in it.