Easy Way to Light Unburned/Leftover Charcoal?

I usually shut down all my vents after I'm done cooking. I then save the un-burnt charcoal in a separate container. The next time I fire up the grill or smoker I reuse the old coal by dumping it on top of the new coal. Haven't experienced any issues. Saves a little money.

Chris

Unburned charcoal is still good fuel.  I reuse used charcoal in both my Kettle and my WSM.

Kettle for grilling:  I load the chimney with some new charcoal, then leave enough room in the chimney to put the used charcoal on top of that.  Fire it up and use it.  I've cut WAY back on how much charcoal I load in the Kettle to grill.  Once upon a time, I would put just about a full bag of charcoal in the Kettle, then spread hot charcoal over the top of that.  On subsequent uses I'd pick the biggest pieces out and fire them up on the chimney.  Now I only use as much as I need to grill for that session.  There's always some left over, so I put new in the chimney and add the used on top of that. 

Kettle for smoking: The used charcoal is my first layer in my baskets, then I add wood and cold charcoal on top of that.  On top of the cold charcoal I'll add only as much new hot briquette as I need to reach and maintain my chamber temp.  

WSM: I keep track of which smokes by date of the last time I emptied my ash bowl.  I can easily go 20-24 hours of smoking before I need to empty the bowl.  I start each smoke by knocking the ash off the used charcoal, then add some wood on top of the used charcoal.  I'll cover the used charcoal with new briquettes, then add more wood.  I add hot charcoal to the middle of the pile, then once the smoke has stabilized, 30-60 minutes, I'll add the meat.

Based on the three ways I use used charcoal, you can figure out which works best for your smoker.