As soon as the stage starts, two Shibalien Elites spawn. 10 seconds later, General GreGory spawns. 40 seconds later, Youcan spawns. About 70 seconds later, another General GreGory spawns. When the base is at 99% health, a General GreGory spawns. General GreGories and Shibalien Elites are spawned at mild intervals throughout the stage.
Using Barrier Breaker Cats (Space Cat, Fencer Cat etc.) helps a lot, since YouCan has a 266 000 HP barrier. Also bring units like Seafarer Cat, Juliet Cat and Corrupted Psychocat to debuff YouCan. For attackers, bring Macho Legs and Chill Cat. If you have any anti Alien Ubers, bring them. Anti Shockwave Cats can also help a lot. With all that, YouCan shouldn't be very hard to defeat. Once he is down, just kill the GreGories and Shibalien Elites and kill the base.
NOTE: DON'T bring Octopus Cat. Though it can block shockwaves, it gets OHK by YouCan since it has shorter range, unless he is BOOSTED. Cat Machine however, is really good. It still has shorter range, but it is resistant to Aliens which lets it survive a lot of hits from YouCan AND block of those shockwaves