Would definitely advise bringing rich here due to the limited cash you get throughout the startoff. You want to start building your LD/wave stack ASAP so you have enough fire power to take down the Chibinels, and quicken the rate at which you kill Red EnerG. Uril is going to be your main staller of Old Horn. Use Breaker Blast whenever the enemies are uncomfortably close. Breaking the Ultra Baa Baa shields doesn't really matter because Old Horn already serves as a wave/LD stepping stone anyway.
Manic Eraser 44
Eraser 20+60
Green Shell 37
Manic Macho Legs 40
Can Can 40 (Bounty, Move Speed 10)
Jelly 40
Housewife 37+3 (Savage Blow 10)
Hermit 35
Uril 30
Naala 35
Breaker Blast 16