I've always used a Dremel cutoff and bench grinder to clean the edge of the casing and one of a couple smaller nails to clean the opening..

However, I recently bought a pair of Hozan C-217 after reading so many people here swear they'll cut evenly. I found that on at least 50% of cuts I don't need to clean up after. Amazon has them for ~$32 right now: https://www.amazon.com/gp/product/B002OFW5Q6

Two other things to say: One, I've only used the Hozans on a couple dozen bikes at this point, so my long-term feedback is limited. Two, I hear the vintage VAR cutters also will cut as cleanly as the Hozans. I just haven't managed to snag a pair at a reasonable price yet to confirm.