If you don't have reservations against dying early and often, I'd say spam rockets at enemies (mid-range and closer) to get a feel for the rocket's trajectory/speed. You'll learn how to lead them better.

Additionally, aim closer to enemies' feet. You're more likely to hit them, and if you miss they'll still be hurt by blast damage. More importantly, hitting their feet directly slows their momentum for a quick bump straight upwards. You can either follow up with another rocket or a few shotgun blasts (get used to Q for switching!).

Lastly, prioritize Nazis and other fash. They don't get to enjoy things.