God forbid you should get some actual experience prior to being and airline pilot. Just in case everyone forgot, when you get hired by the airlines, you will have anywhere between 2 and 70+ people's lives in your hands. You are not sitting in the right seat to get instructed. Yes, you will learn a lot, but you are not there to fly and screw up under the umbrella of the capt's ATP!

Flight instructing/flying cargo etc. is NOT "time building". It is probably the most valuable experience of your flying career.