Use the following trick to get the Bolt Multiplier to 20X and earn lots of 
Bolts. To do this, you must have completed the game at least once so that you 
are in Challenge mode. Go to the Battle Arena on Planet Mukow, and choose the 
"They Were On Sale" fight (with the hundred bomb bots). Once the battle has 
starts, use a Mr. Zurkow, then start throwing the Nano Bugs (small turrets that 
shoot bugs). Next, use any weapon to kill what does not die from the turrets. 
The Pyrocitor is recommended if it is level 6 or above. Do this three times for 
your Bolt Multiplier to be at 20X and get lots of Bolts.