After a long wait, I finally finished my first all-foil card, the From the Vaults version of Rith, the Awakener. When it comes to 3Ding, foils present a number of difficulties compared to regular cards. Two big ones are:
1) Foils are much harder to cut, so doing fine details is very difficult.
2) When you cut open a foil, you expose not only the inner white (which normally is easy to color away with a pen) but also the plain foil layer (which can't be colored away with a pen). This makes edging tricky; some spots will have shiny dots or lines because of the foil peeking out.