I moved my brewing out to my garage when I went to AG. I had similar concerns.
I swept the cobwebs off the ceiling but other than that, nothing special. I brew with the door wide open. I just make sure that I cover the brew pot with the sanitized lid, the moment I turn the flame off. All of my plumbing from the brewpot to the chiller to the carboy comes straight out of the Iodophor solution prior to connection. I make a double hood of santized tinfoil to cover the carboy opening. I pull the hose from the carboy leaving the foil in place. Repeat the above for oxygenating and dumping the yeast starter. Every time I touch the foil cover, I hit it with spray sanitizer first. I pull the closure and blowoff hose from the sanitizer and install as quickly as possible. The carboy sits in a tub of water in the back of the garage. Believe me it's dusty. I do throw a big towel over the tub. The environment is never perfect, but with a little care, you can minimize the exposure to all of the critters.
Primary: , Boddington's Clone, Mirror Pond w/Marris Otter
Bottled: Fullers ESB Clone
Kegged: Mirror Pond Clone
Drinking: BM's Kona Fire Rock, Dead Guy Clone, Alaskan Amber Alt Clone, Firestone DBA Clone, Magnum/Crystal IPA
Next up: Burton IPA