Rather than rushing a production with huge amounts of money or wasting a valuable leader, just build a unit (such as a tank or something that needs more shields), and move it into a city that's production you want to hurry. After that, disband that unit and it will turn into a certain amount of shields. Repeat this process until it is done the next turn. Note: This doesn't work on small or great wonders.
Build a pretty big fleet of planes consisting of five or more bombers, fighters, stealth bombers, etc. Then, put them all into one city and build a carrier. After that, move the carrier into the square you want to land the extra planes that the carrier cannot hold. Finally, press the button that moves units of the same type from that stack (located above the info box) and land them on the carrier. Now move the carrier and all the extra planes will be flying in the middle of the ocean. Note: The planes will remain there until you tell them to move to another place.