You can find a pair of cordless clippers for rather cheap ;) Clippers are good for a many things, so investing a little bit of money in them would be worth while. I tried roaching my horse with scissors, absolute disaster. It was so choppy, uneven, and ugly. I had to bust out the clippers. A mans razor wouldnt have a chance against a horses super thick mane, and it probably wouldnt do any better than scissors. I guess if you can't get clippers, then scissors may be the only option... Ideally clippers would be the best though... Maybe if you can't buy one, you could rent one? From a dog grooming place or something?
If you are strategic about it scissors aren't really that bad to use. Just be prepared to snip some off here and there for a while until everything is even. I attached a picture of my friend's horse, who had a mane that was all rubbed out from their round bale feeder, which was made for cattle, so I took the scissors to him so he'll grow it out all even before he goes home to rub it off again. I did leave the only long section on his withers as a a bit of a joke. (One time my friend and I were riding, and when we got back we braided the horses manes. She was riding one of my mares, who had a god awfully thick mane and put about six huge braids in it and left right by the withers unbraided. So I left her just enough to braid, but his poor little 'rat tail' never gets braided.)