TCP or Decolin added to the fuel is the most effective way of reducing lead fouling in my experience. It converts the lead to a powdery salt that won't accumulate. It also has the benefit of keeping fuel valves free-turning; that may be anecdotal, but true in my experience.
REM37BY plugs and the fine wire (expensive) versions are more resistant to fouling, but not immune. You need to check which alternatives are valid for your engine.