removal of lint build up

I am trying to clean all the collected lint that is under the lint screen down in the bottom of the cabinet. I have removed the two screws on the outside and the two on the lint screen housing inside the drum and cant seem to get the housing out. What am I missing? I just want to clean it out as I know its a fire hazard and I normally blow out the vent every few months to keep the dryer well vented but I dont want to have to call a tech because I caused damage while trying to prevent it.
Please advise.
Thanks, Wen~