reading around online i found a lot of solutions that i couldnt do or that didnt work.
first i tried:
dremel with cutting disk. this burns your wood edges, doesnt cut well, and you cant go straight down with it. no control.

a small router bit, with a 2x4 guide. this worked surprisingly well, but the start hole when you first put the router in always was a little off, and the slot was a tad too wide for my taste.

anyways, i have been working with no drill press, limited router stuff (only freehand abilities), and overall a shortage of tools. but here was my solution, and it first absolutely as perfect and snug as you can get without being too tight for the switch. i only found this by breaking a tool first =D

FIRST, im working with 1/4 inch spruce here. draw your straight line where you want it. take an exacto knife, make sure your wood is pretty well supported from behind, and that nothing important is underneath it
using the exacto knife vertically, push straight down into the wood, perhaps with a slight paper-cutter motion to get it to work all the way through. once the tip is just through, pull down as if you were using a paper cutter, so it forms a slight cut in the wood. it wont be very long however, or wide.

SECOND, take your exacto knife and do the exact same thing you just did, parallel to the first cut, over just a TINY bit, i mean about the width of the switch part that comes up through the wood.

THIRD, using your exacto knife, poke out the little piece of wood between your two cuts, so you can see through it.

FOURTH, using a jigsaw wood cutting blade, NOT IN a jigsaw, you are going to cut your slot by hand using the blade as a saw. cut the length of your line, whatever you need for your switch.

FIFTH, turn the jigsaw blade around, and go over the area you started with your exacto knife once to even it out.

you should now have an easy, perfect, straight slot for your switch to come through!

video to show how: