Since people starting writing mods and using console commands. Perhaps I should have used the words "the correct way".
The correct way? Really? It's an Elder Scrolls game. People will play this single player game how they feel like it. If people feel like cheating and it makes it fun for them, more power to them. But to say that you should have used the words "the correct way"? That's just incredibly close-minded. This is especially true for this type of game.
In any case, it's not really all that difficult to level any particular skill from 15 to 100 even without spending a single perk point. Some are more difficult than others, and by difficult I mean more time consuming, but this far into the game's release I am sure that many people have reached level 81.5. It's not that difficult to do, just time consuming.
It really didn't take me all too long to do it myself, and that was on my first play through of the game (Without paying for training mind you and on Master difficulty). Having some prior knowledge of Skyrim sure could have sped things up here and there (I.e. not a blind play through). So yeah, it's not really difficult to do and it's easily in the realm of possibility. I suppose if you consider something time consuming to be difficult you might find it a bit difficult, but aside from that, not really difficult in the slightest.