Amber SHELLAC-dealing with small water stains first.

One small container will do a lot of wood. 

This is how I used it:
Sand the area to bare wood
Clean off the dust with a dry cloth first, then a tack rag you can get for $2 at Lowes or Home Depot.
The instruction say to mix a heaping tablespoon with a quart of hot water. I went a little stronger for the test...maybe a teaspoon for a cup of hot water. A quart is all you need for a camper with a lot of staining. Mix half for just small spots, it doesn't take much.
With an old toothbrush, gently brush it on for 20 seconds or so then wait 10 minutes. Reapply if you want it lighter, but one treatment got me the results you see above.
For really small areas, I'd put it on with a Q-tip. 
Try not to treat beyond the stain area, no need to bleach good wood.
The instructions say to "Triple rinse" the area with water mixed with a little baking soda. I wiped it (only in the stain applied area-a quart of water with a table spoon of baking soda) and pat it dry with a cloth. 
Wait until it dries completely and sand with 220 grit paper.'
Done!

In my opinion the key is to be very strategic about applying it. Try not to get it all over the place. When you apply both the cleaner and the water to rinse, make sure it doesn't run down the wall. If it does, you're putting it on too heavy. After one spot you'll understand. No need to soak the area, just wet it. The toothbrush and q-tips will help. Wear gloves and goggles. Treat it the way you would handle straight bleach.