Special interests will always find new ways to help their friends on Capitol Hill. Mere laws can't stop it; look at how pathetic campaign finance reform was in practice. In my estimation, the only way to keep specific individuals, groups, businesses, and unions from buying congressmen is to greatly reduce or eliminate the power of congressmen to impact those special interests.
Much of that power to fiddle with specific sectors of the economy seems extra-constitutional to me anyway.
increase the house ....1:50,0000 representation =6000 congresscritters. Make the senate appointed by the states legislature as it originally was. Pass term limits , make ALL financial interactions with our public servants transparent at every level...this alone will facilitate term limits. Make all congressional travel and schedules public..ALL meetings which they attend open to public....(obvious national security exceptions!).....just a few ideas!!