Many places do not allow pyro, as airsoft grenades are 99% home made, and the possibility of injury, especially hearing loss is very high.
Games that do allow, are usually few and far between, but when they are, its usually a good idea to give a demonstration to everyone before the game, and if anyone has any issues, they dont get used.
A paper tube, with a firecracker charge(a large one) inside filled with dried beans(cheaper then BBs and biodegradable). taped shut.
Still, it can be troublesome as we dont use pin-pull grenades. Having to pull a tube out, pull a lighter out of your rig, try and light a fuse(wind, rain can fuck this up) then toss it with a rig on and somehow not dropping your AEG can be more trouble then not.
For safety reasons, its good practice to give a notice before you toss the pyro....and you dont toss it directly at someone, just near. Shouting "GRENADE" or some other phrase several times before tossing helps notify the other players of the danger sailing their way.
Asking when it should be used and if it more effective...well, you can decide on that yourself....its kinda like asking is wearing pants in public is a good idea.
this is a good thread to read
http://www.airsoftcanada.com/showthr...hlight=grenade