If the joints fit tightly, as in say, ribs to spar, then a couple of drops of thin CA on each joint is plenty. I have never added fillets of Medium and have never had a joint fail. In my opinion, adding medium after the fact is a waste of time and money, and only adds weight. (Build to fly, not to crash.)

I have tested these joints and the wood will tear away before the joint fails.

Try applying a couple drops to a joint and watch it closely, it will "wick" along the joint, and travel a surprisingly long ways.

Definitely get the long thin tips for your CA bottle. They allow you to apply the glue more accurately, and you'll waste less.

Any of the name brand CA's are good. I've even had good luck with some "house" brands. It's really a matter of purity. The best I've used to date is Jet thin CA. I had a 2 ounce bottle that lasted through construction of two planes, plus some repairs, over an 8 month period! No special storage other than replacing the cap immediately after every use.
Dennis-