Since the game is relatively easy on brutal, i'll just be talking about the extremely hard parts; meaning the RTS style battles. First, you wanna make sure you don't get overwhelmed. Always have some units on the battlefield. Second, you'll wanna rush your opponents stage as quickly as possible. Kill them before they have a chance to regroup and attack again.
Now here is a guide for the battle with Ophelia at the Sea of Tears. This isn't a glitch, but it is a little cheap so use only if you're desperate like I was. First, on your side of the bridge, take control of all the fan points. You'll wanna have the homing missiles on your Deuce as well. After taking control of the fan points, summon up as many units as you can. You'll also wanna upgrade your stage all the way and summon one rock crusher. Upgrade your headbangers and razor girls if you wish. After everyones all ready to fight, set up a rally flag (if you haven't gotten this solo might want to) right before the bridge. Every now and then a small wave of Grave Diggers and Reapers will appear. Let your men take care of it. If a lot of your men die, simply summon more and they'll move to the rally flag.
Using Eddie's fly ability, fly AROUND the electric towers where you'll see a small army of enemy cars, a balloon, some ground units and the tree. Fly to a little spot as far as you can away from them and summon the Deuce. Using your homing missiles, fire away! If you hit the cars, most of the time the other units, even the car you're hitting, won't react. Just keep firing. If your car gets destroyed just start wailing on everything with your axe until you die. Check on your units often, make sure they don't all get killed, summon more if you must. Keep flying and shooting missiles at the enemies until they are all dead.
Once dead, take your units up the bridge and destroy the other small army standing in the middle of the bridge. After they're dead, regroup with more units and take out the two towers powering the lightning on the bridge. After that, bum rush the stage! Send all of your units to attack it. Double team with the headsplitter or the Rock Crusher to make things go by quicker. Set up a rally flag right by Ophelia's stage if your units start dying. Just keep firing on the stage and it should go down quick.