straight edge for router

Hi,

i am Installing zenith compact laminate worktop and i will only need to cut straight edges, so don't see the need to spend £80 on a worktop jig

What's best way to make a straight edge for the router? Would 18mm MDF board work?

I have bought 1/2" router bits and also a guide bush

I am assuming the guide bush runs along the edge of the straight edge?

First time using a router

Cheers