go for it man
don't lose yer hope

It's not that hard, really. Once you do it the first time, you'll be able to beat Wadolf without even getting hit once.

First, save all of your guts for the last fight, to recover from Jeff and Stamper. You should not need them until this point, especially when you get a 100% health restoration from the slot minigame (in case you haven't gotten it, jump on the middle button once and the right button twice).

Secondly, remember that Wadolf (and every other enemy) only hits you if you're on the same horizontal axis. Staying a little bit above or below their horizontal will prevent them from attacking. Be warned that the laser attack has a large vertical range, though.

Third, ignore the zombies. Try to lure them to the top or bottom of the screen, and then just go after Wadolf. Smack them around until they flinch if you're a slower character, but remember that the boss will always summon more, so going after them is a waste of time (unless you're going after the Horde Fighter medal).

Lastly, if you get hit by the laser, frantically slam the bomb button; you might get lucky and toss a bomb that will interrupt the attack and hurt Wadolf in the process.