[dsraven]

like the way you did the inner fenders, not just cut off raw edge, actually bent over on the new cut. looks good. whenI did mine I made sure to bring the suspension to full jounce, like bottomed out on the snubbers, then cut the inner fenders to clear the control arms etc. my cut way is waaaay bigger than yours though.
something I have found to work well for filler is the worn out, thin, flexible but still holding a good flat edge, steel putty knife. I have several in different widths. I usually try them "dry" to see which will give the best contour for the area where the filler needs to be applied. then mix a small amount of filler and apply it. I use USC featherite. don't add too much hardener and then you have more work time. apply it, leave a small amount somewhere you can check the cure, smooth it, keep checking your "test cure" spot, let it sit till it is nearing the no return stage. smooth and come back later. if sticky, wipe with laquer thinner, wax & grease remover or reducer, let dry, then sand and spray high build. downhill from there.