Asking for tips on getting mastery badges

I’m doing campaign for Excalibur, trying to finish all mission lines with honor. I’m stuck at Alliance-15 and Union-15 now. I’m a below average player with overall win8 at 950, but I’m improving, recent win8 is above 1100. To me, getting M in a game is solely based on luck, when all stars aligned. I have around 10 M badges unintentionally and I’m sure I don’t know how those happened nor how to repeat them.

I’m trying to get 3 M for Alliance-15 with honor. I checked tomato.gg and found requirement for Super Hellcat is quite low for NA servers (1100-ish). Been playing it for last 2 weeks, couldn’t get above 1k exp per game.

So for a TD like S-Hellcat, paper thin armor, mediocre dpm, how do I play it to get more exp? I can’t outspot the LT to get more asst. dmg. What are the tricks or tips to enhance exp per shot or per minute in game? Equipment? Crew skills?

Thanks for reading and giving advices guys.