During the official Employee Pricing event, dealers would offer the EP, the financing rebates if you wanted to go through Chrysler Capital (0% incompatible with EP), and any conditional rebates like your First Responder. Some people had Private Offer coupons, something you might get as a pop up while browsing the corporate website.
Unless your conditional rebates were abundant, you could not get 20% off. I think 16% was closer. However, if you read this thread, *some* people ARE getting 18-22%+. There isn't much known about how to do that in a clear-cut, never-fail way. I am guessing that dealers may have scenarios that will lead them to discount further. Old stock, overstock, unpopular configurations, trying to hit a sales goal. Buyers who succeeded in getting deeper discounts aren't often reporting exactly what the scenario was.
There is advice about end of the month, end of the quarter, holiday special event, being aggressive or defiant, walking away. But a dealers have policies and true costs. They're not in business to lose money. Further, behavioral tactics won't change the facts on the ground. That is to say, you can't throw a fit to get your way if the dealer can't meet your price.