GAM makes a product that is designed for exactly this kind of torch effect.  It will even pass a fire safety inspection in strict cities like Philadelphia, which is where I was involved in this production.

 

 

That's a link for where you can buy it, but there are also some rental companies out there that have the whole torch package assembled and ready to rent.  They all use this as a base though.  It's the safest "live flame" way to go.

 

If you are building it yourself, consider strongly doing something with fake flame.  Lighters are likely to look so wimpy it won't be worth your time.  You can get fabric torches (http://gallery.bcentral.com/GID5064795P3771799-Fake-Fire-Flame-Lights/Fake-Torch-Battery-Operated-Flame-Light-Fire-Torches.aspx) that look quite nice from the audience, and are much safer than anything you build that will produce a beefy enough flame.  They might not look completely realistic, but my guess is that most of your costumes have a cartoony feel too, so it will fit in fine.  Also, you won't have to worry about the fire inspector shutting you down.

 

Laura