Great recovery! Having just spent an afternoon masking and painting the red bands on my DVII only to have them both too rough, and in the wrong place, I know how you must have felt earlier!
I used Mr Mark softer on the trailing edges of my Aviattic decals on my 1/72 builds, this somehow makes the edges brittle and allows for easier trimming with a new scalpel blade. I suppose Extra Thin will do the same, but might be a bit hotter (though don't let the Mr Mark stuff pool too long as well, as it will melt the printed surface!)
Jeroen