I have verified the blend door is opening/closing and when switching to defrost I get air from the corner vents on the dash however very little/if any comes out on the windshield. Is there an easy way to clean these vents/ducts?

Background...some field mice made themselves home in the vents/ducts prior to me owning it. For the first 6 months I had it bits and pieces of carpet pad would have to be pulled through the AC vents as it would blow in behind them.

1993 Ford F150 Supercab XLT 5.0 4X4