Blacksmithing questions?

i lately build a forge out of a steel strainer and mud and it works good. i can get metal to about bright orange in a couple minutes. my forge burns through coal quick, about a big hand full in 2-3 heats. is this normal? and also what can i do to make it more efficient . the forge is small a little bigger than a Coffee can. for the air source i use a hair dryer.