I agree with others this generally sounds like a bad idea. In the hay day of Farmville, people where I worked used free proxies because the Co. had strict rules about chatrooms/playing games. The problem with free proxies for poker is they frequently went down or you'd get disconnected. I wouldn't want to be in a mtt/stt and lose my connection.
Seems like install/uninstalling poker client would be a big pia to cover your tracks after every session, not to mention they could have spyware on your terminal.
Maybe if you got a reliable paid proxy service and played using the flash player tables that some sites offer then you could do it. If a site prohibits proxies, and you have a private office, then use your personal laptop that is tethered to internet via your personal cell phone.
I'd have to seriously question my motives for wanting to do it and think maybe I had a problem. Unless I had a lot of downtime at my job and/or a spouse at home that hates online gaming.