When battling the Scorpion Queen in the 'Dismember The Alamo' level use your grenades to help defeat it. You will need to time your jumps when it fires it's machine guns and attacks with it's tail to avoid them. When the Scorpion Queen is on the ceiling try to remain underneath and shoot up.
Avoid the rockets in the 'FU, Too!' level and when Rhinozilla charges jump to higher platforms. Shoot the green lights on his nose and chest until they explode and shoot Rhinozilla's mouth when it opens to expose the large gun barrel. If you can't get away from the rockets that Rhinozilla launches at you just shoot them.