once a week, occasionally twice a week. Doing 10-30m sprints on grass. Volume was low, as was frequency, wasnt taking this too seriously. In fact the sprints were more of a warm up for the lifting.
when I got more serious about the speed training, it became workouts such as 2x20+6x60, 6x FEF, flys, 20s30s40s50s, etc etc the emphasis had certainly increased a lot.
And when talking about plyos, vertical plyos will aid max. velocity sprinting the most, as compared to more horizontal jumps.
so depth jumps will do more for your flying sprints, whilst broad jumps will do more for your acceleration.