When you are using medium or thick ca, squeeze the bottle a little bit while it is still right side up. Then while still holding the squeez turn it upside down and apply your ca like normal. When you are finished and you let go of the bottle, the extra suction pulls the ca out of the tip and keeps it from getting clogged.
Also I wipe the outside of my tips with hard paper like one of those cards in magazines. That works a lot better than soft things like paper towel