You can get plenty of Mojo by traveling through the three teleporters at Mount Grimly. Take the mutant you want to upgrade to the three teleporters, then get the Grimly that is respawning in the east and enter the left teleporter to Wumpa Island. Jump carefully on the stone bridge to the left and walk the southern route to Crash's house until you meet the Slap-Es. Now slow down time and attack the Slap-Es with the Grimly's boxing attack. Keep beating them up, even when they are on the floor, to build up your Mojo multiplier. Once all of them are gone, teleport back to Mount Grimly. From there you can teleport to Wumpa Island again and repeat the process until you have a multiplier of 20. Back at Mount Grimly, take the teleporter in the middle that leads to the Wasteland. Once there, destroy all the cactuses to get a large amount of Mojo. When there is no cacti remaining, teleport to Mount Grimly then go back to the Wasteland. All the cacti will be waiting for you again.