This is pretty straightforward, but just a few things:
Do this in Skirmish.
Don't do this with Strongholds! The enemy just spams units and it's annoying...
Do this with the Skull on that gives you a free tank and infantry every time you lose a base.
Pick Deathmatch, 9999 resources, an Easy enemy AI, any map, and the Skull AFTER PARTY.
Any other helpful Skulls, and NO Fog of War.
When the match starts, quickly build on all the build points around the map, then as soon as they are built destroy them, especially the ones closer to then enemy, select all your new tanks and troops, send them close to the enemy base, then attack! Make sure to take out defensive buildings. The AI will probably put up a fight for a bit, so do try to micromanage and bring in reinforcements if necessary!
Keep destroying bases if you need to for more tanks!
Enjoy!