I use a pair of needle nose pliers to hold the sprue and then twist the jig back and forth to break it off. I either scrape with an old pocket knife or smooth it with a little file I have. On my horse heads sometimes you'll get a little lead on the upper arm of the swivel and I use a box cutter knife to trim it off.
Any flash you can use the pocket knife on.
I have gate cutters for troublesome ones but if you cut too far you'll leave a big flat spot on your jig.