I'm not saying it's easy, but it's not too hard. And I did point out, atleast I think I did, that it is pretty hard at first. Soley because one will find themsleves leveling before they even cap their main weapon, let alone a second weapon. This only applies pretty much till around lvl 15-25 or so, about the main weapon. Around that time you begin to cap whatever weapon you've started with, in exp parties, and once it's capped your can probably always cap it before leveling again.
I thought ahead of that though. As the above situation doesn't leave any room to really start leveling that other weapon. So.. when I went through on Warrior (beginning job) I knew I wanted to be a Drk and that I wanted to level GS as well as scythe, so I used GS on warrior all the way up to 40 (and tanked no less, with /mnk, and I didn't suck. Booyah!) So that certainly spared my having to worry about even leveling GS up untill around the late 30's on Drk, by then it was really no problem. Only around mid 40's I was really soaring through levels at that point, and GS didn't get much use so it went into a slump as my Scythe skill surpassed it.
I dont remember exactly when, I believe from 54-55 I decided to go and skill GS up by myself, it took a long while.. but worked pretty well up to a point (fought beetles in Eastern Altepa at the zone line). Before I skilled up, using a GS in exp parties was pretty much constant wiffing and maybe a hit here or there (this is when you switch back to scythe and give up temperarily). I got it up to eventually about 15 points away from it's cap at lvl 54 skilling it up solo. After this point I noticed I didnt miss nearly as often as I started to bring it out in exp parties to test how it was doing. It couldnt do the dmg my scythe could, but I didn't miss with it any more than what was usual, so I was able to use it in exp parties and had it capped by the end of lvl 55.
Completely viable option, just.. dont suddenly switch. You have to let the rest of the party know, and find a new skillchain to use. 90% of the time if you do this no one is going to argue, because you can still go on doing the same thing, just using a different skill chain/burst. If they do argue against it, don't worry, stick with scythe, there are other parties that won't care because you'll still be doing good damage and they'll still have a skillchain/mb to use.
Another piece of advice I didn't mention, if you have to skill up GS like I mentioned, switch to GS only after capping scythe already. In the mid level range, there are times where it may take your scythe a while to finally cap before you level, and it's far more important to have scythe capped at that point in the game, but that doesn't mean you should slack on leveling GS. That's all im saying. 8)
:lol: 
