How to enforce that congress does its job.

Congress has it all backward. They made sure they get paid when the rest of the government shuts down. They should only fund themselves until June and then go without pay until they get the budget completed. To be fair, the office of the President should follow suit a month later if he has failed to sign the budget presented or a submitted a revised one in compromise. So both are on the hook until upcoming fiscal year's budget is signed into law.