Newt should be answering this but I hear he's out shopping for a new truck and is having trouble with the colour.
I think of snares as blind sets which are somewhat species specific. For a blind to be successful it must be in a traffic lane (the more traffic the better). Also, in my opinion snares work best when you get the critter "day dreaming". Having said that I would not use any lures in conjunction with a snare. Only you can determine with what regularity the critters are hunting the bales. You will probably have to use two snare loops and heights, one for fox and one for yotes. Pick bales which put the snare on the dark side (relative to the moon) to help conceal them. I often hangsnares over trails which have no cover but perfer brush etc to help hide things; hay bales sound pretty good to me. As for your tracks the less the better work form the side of the bale opposite the loop and use the same route. Also, killing snares would be my choice to help with repeated catches in the area (Ambergs or similar locks). Anchor them solid!
I think of snares as blind sets which are somewhat species specific. For a blind to be successful it must be in a traffic lane (the more traffic the better). Also, in my opinion snares work best when you get the critter "day dreaming". Having said that I would not use any lures in conjunction with a snare. Only you can determine with what regularity the critters are hunting the bales. You will probably have to use two snare loops and heights, one for fox and one for yotes. Pick bales which put the snare on the dark side (relative to the moon) to help conceal them. I often hangsnares over trails which have no cover but perfer brush etc to help hide things; hay bales sound pretty good to me. As for your tracks the less the better work form the side of the bale opposite the loop and use the same route. Also, killing snares would be my choice to help with repeated catches in the area (Ambergs or similar locks). Anchor them solid!