Trying to burn coal with the front doors open isn't going to help. Instead of pulling air through the coal bed, you pull it through the doors and up the chimney.
You are on the right track with the gaskets, get the stove sealed up the best you can. Every leak you correct will help get a good draft through the coal.
What are you using to start your coal fire? Wood? Charcoal? It is important to get a good hot fire going before you try and add coal. I prefer to use newspaper and some small kindling because it helps warm my chimney and start a good draft.
There are lots of threads on how to start a coal fire in the hand-fed stove section of this forum. There are also some decent guides on other websites, a quick good search brought this one up: http://www.woodmansforgefireplace.com/F ... sp?id=1650