50,000 words is only 1667 a day. It's time consuming, but not out of the realm of possibility. I probably have enough words just in the "Going Natural" forum, but that's not the point...
You can make up your own words. A couple years ago I took Hawaiian words and chose the OTHER set of consonants... instead of K, L and P I used T, R and B - like some of the old maps, before the spelling had been settled. It slowed me down a little, but by the time it mattered, I wasn't using any new words. So kapu -> tabu, etc.
I'm a little ahead of pace right now. I've never been ahead - one year I didn't even start until Nov 12, and had to write like a maniac.