stale gas

So I have drained the tank. Pulled it and got all of the fuel out. Plan to drain fuel lines, fuel water separator and fuel pump. Drain and clean carb bowls and passages. Fill with new gas and see what happens. The question is, do I need to go crazy cleaning the gas tank? As in use an industrial degreaser and power spray what I can? I'm not seeing or feeling any coating or varnish on the accessible tank surfaces. I would be stoked to hear what anyone else who has had stale gas has to say. 

I have it all apart so it would be good to do what I need to do :) 

Hmm, will find my compression gauge and check the cylinders today. Seems like a good idea.

I had to clean out a tank with old gas in it a couple years ago, couple years old gas not 6 mos, I only had so many containers to hold it, I had to pull 40 gallons.  When the tank still had a few gallons left I dumped the last 3 gallons into two of my own cars.   Both are fuel injected engines, one was a 2003 Yukon the other was a 2012 GMC.   Just the gallon and a half in each caused the engine to run rough and I had check engine lights popping on till that tank was burned up.  Did no damage but I had to put up with lousy running engines for a while.   My boat sits 6 mos without use almost every year and I do not worry about it.  No problems in a FI GT40 so far.   I do try and park it for the winter with premium fuel in there because I figure if it degrades it might still be OK to run but some years I forget and park with regular fuel in there.