Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave
oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna?

There are tons of "pringle" or coffee can antennas or similar on the web.
For example: http://flakey.info/antenna/waveguide or
http://www.turnpoint.net/wireless/an...coffeecan.html

I suppose one need only insert the magnetron antenna into the coffee can
where one would normally mount the N-connector feed point.

A labeled diagram of a microwave magnetron can be found at:
http://www.gallawa.com/microtech/mag_test.html

I suppose the metal coffee can has superior micro shielding properties
relative to the aluminumized cardboard pringle can.

Would I be better off with plumbing copper drain pipe from the stray RF
exposure perspective?

Since microwave magnetron use a half wave power supply, can I use two
magnetrons in the same coffee can powered from a single AC HV transformer
with a pair of HV rectifiers to feed alternate cycles to the magnetrons?

Greg, VE0ACR