I'm sorry but some of the advice here is bad. Telling them to just use their brakes, no mention of matching the gear to their speed? What happens if they're stopping for a light and it suddenly goes green, but they're in 5th gear and now slowed to 20 and applying brakes? They're gonna try to open the throttle and stutter their way through, or slam their way down to first. What if they were going faster when the light changed, are they just going to know exactly what gear to move into? What if they need to perform an emergency maneuver? You should be matching your gear to your speed during deceleration. I'm really not a fan of telling someone to shift down all the way once they've actually stopped, that's stupid.
Search youtube, there should be countless videos about this. I'm really disappointed that Learning Curves didn't teach this skill to you better, I've taken their course and it was covered (though I had previous riding experience). Basically, as you're slowing down and you need to downshift, you pull in the clutch and blip the throttle (blip just means quickly twist {open} the throttle for a split second to raise the engine revs, you're not opening the throttle completely), downshift and let the clutch out. It's written step by step but performed smoothly almost as one combined action. The result of this is engine braking. As long as you're not overrevving the engine on the downshift, the engine will be fine - you can't go from the top of 6th gear and downshift into 5th, you need to slow down first. This isn't a replacement for braking, but it's a skill to apply in appropriate situations. You should know how to do it
Look for a copy of Keith Code's Twist of the Wrist DVD, it will teach you a lot of techniques including the one rmemedic mention, learning the blip the throttle for downshifting while applying the proper amount of front brake.