I don't really like training before the Elite 4, unless i'm ridiculously weak and can't even hope to beat the first member.
Usually i prefer wasting my money instead of my time, so I often use cheap strategies like:
1. Buying a huge amount of Revives and spam them. Pokemon that can't be beaten get PP stalled.
2. Using X-Items. A lot of them. Works perfectly together with a sleep inducer, otherwise it's quite difficult and require a lot of Hyper Potions.
3. Attempting the Elite 4, blacking out and walking in there again. Repeating this until the champion is beaten or the team gets strong enough to beat the Elite 4 using Revives (bought of course BEFORE the first attempt). This is faster training than it would be ever possible in any Victory Road.