The "rule" has always been minnows in the spring, leeches summer. I use crawlers because they're cheaper and they keep easier, and I think the walleyes aren't fussy when the water warms and their metabolisms are going.
I don't know if the key is to get thru the smaller perch or that the walleyes get active and the smaller perch get lost. When I start getting hit by small perch I'm looking somewhere else for fish, usually deeper. I know others on here probably have more/better insight on this.