Pontiac: Pontiac AC vents, blower motor resistor, squirrel cage

Question
Assuming I can locate the blower motor resistor (I assume next to the blower motor, under the hood on the center of the firewall ?); how can I access the evaporator core to clean it out with "Blast" or some cleaner? Do I have to take the dash duct work apart or can I access it from the squirrel cage area or some other way? Thanks :)------------------------
Followup To
Question -
92 Bonneville 4 dr sedan
The dash vents hardly put out any air flow, leading me to believe there is a damper not opening. Increased flow minimally by pulling the air breather tube off the blower motor. Have all 4 speeds and the air is cold enough, but high speed puts out the same cfm as low on my truck.
There are several dampers; how do I identify the
correct one restricting the air flow. No, I don't have much from the floor or windshield vents either. Checked for an vaccum leak but didn't stumble on one even under the dash. HELP
Answer -
First of all, you cant compare the air flow on your car and your truck.
The most probable cause of your low air flow is a clogged evaporator core. It probably has a small leak and the oil from the AC system and dirt from the air are whats stopping the air flow. This is a very common problem on your car.
You can remove the blower motor resistor and look down inside the evaporator case to see if it is clogged.

Answer
Yes the blower resistor is near the blower motor. It is under the relays on the passenger side of the firewall.
You might be able to remove the blower motor to get to the evaporator core to clean it out. I always replace the evap core because if it is clogged, it is leaking.