In theory, yes it works. In practice, not really.
Smeargle is extremely frail, and will often get knocked out in 1 hit. So, you generally need to make it hold a Focus Sash just so it gets off one Geomancy.
Let us say it does survive 1 hit. Further, that isn't enough, because if you're slower after the boost, you'll be knocked out, or any priority move will also KO it. And if you're faster, Mewtwo will come onto an attack and lose health unnecessarily.
There is some hope, though. You can run Spore over Recycle, and guarantee one turn of whatever move you want to use. Use this with caution, however, because if you don't run Focus Sash, it will work only if your Smeargle is faster than the opponent. Due to poor defenses, both Recycle and Recover are wasted on it.
A more successful set would look like:
Smeargle @ Power Herb / Focus Sash
Timid Nature (+Speed, -Attack)
- Spore
- Geomancy
- Baton Pass
- Sticky Web / Stealth Rock
In fact, I distinctly recall being run down by a team of Geo-pass Smeargle who passed it on to Mega Blastoise who promptly Water Spouted on any chance I had of winning. So, it's a bit uncommon, but you can run with the set, specially if you're up against a defensive Pokemon like Blissey to use as set up fodder.
