I have a safety razor as well that I use when I've got both time and the need to shave, which honestly happens once in a blue moon. Even the safety razor takes considerably more time than using a cartridge type. I cant imagine the time and focus you would need for a straight edge.
That and I shudder to think of the damage you could do to your face with one careless stroke. When I first started using my safety razor there were a few times where there was seemingly no end to the bleeding. Unfathomably sharp.
Rockwell's comment about almost hitting bone made me cringe, mostly because I absolutely believe him.
Good luck though! Youtube has some tutorials if you are feeling froggy.