Fitting a switch or a socket to your newly modified console can make a big difference. It a real shame to see some real ugly switches fitted extremely badly, ruining the aesthetics of the machine (another reason why switchless mods are a favourite of mine!). Take your time, as with all modifications, practice on something else first.
I prefer to fit slide switches where possible, I just prefer them over toggle switches. But they are more difficult to fit. I usually buy a spare switch, just so that I can take it apart leaving me with a shell I can use as a template.
Hold the template in place, and use something to mark the screw holes. Drill them out and then screw the template in place.
Now you can drill and file the rectangle out and it will leave a perfect size hole for the switch.
I try to do the same for sockets, finding or making a template. Such as the VGA socket used in various guides. I grabbed a broken PC graphics card and did the same, drill out the screw holes, then drill and file out the main hole. These pictures explain it better.