I just built dragonite workshop. Do you have to keep constant production?

Dragonite production requires gold and takes time to process. You don't have to do it constantly but building up a stock of dragonite whenever you can is useful for parts crafting and specific building upgrades that need it.

Rush production is an option to get some dragonite produced immediately. It will take your remaining gold that is in the building and immediately turn it into dragonite but you will only receive half of what you would have done if you waited.

So if you are producing 100 dragonite over the next few hours and use the rush production it will use up all the gold immediately but only give you 50. If you use rush production again before the daily reset then this time it will give you less than half. And each time after that even less. Rush production is really only there to get you a few extra if needed for an upgrade or other activity right now. Don't use it otherwise.