Considering the pressure the Cline can put on a tank it's not surprising that you have as much of a mess as you describe. You said the stopper came out of the tank. Did the stopper come all of the way out of just loosen up in the neck? If the stopper came all the way out I would bet that the result would be very much like popping the top on a shook up, warm soda can. All the pressure in the tank attempting to escape all at once in an instant, carrying the fluid out with it, makes a pretty big mess when it happens. I would bet that a lot of that fuel escaped out of the tank neck hole in the firewall and made it to the exterior of the plane causing the mess you described.

I opted to use a Sullivan stopper on mine, the plastic disc's and sheet metal screw are far less likely to loosen up over time and with vibration. I also think that the rubber GP is using for the stoppers in their ARF tanks is prone to shrinkage with time, resulting in the leaks and other problems many of us have experienced.

I'm not sure about the spray your talking about but a trick I have used very successfully is simple floor dri compound, you know it as the stuff mechanics pour on the oily spot on the floor, it is NOT kitty litter BTW. Whenever I have a tank leak in the nose of a plane I just pull it out and fill the nose up with the floor dri and stand it in the corner for a couple of days. The compound is VERY adsorbent and will literally pull ALL but the minutest amount of oil out of the wood. The only drawback to using the stuff is that it takes time to do it's job so patience is a virtue when using this method. You can get the real stuff at most auto stores and it's usually pretty inexpensive.