Okay to combat taunt you could give your Smeargle a Mental Herb as a Mental Herb removes the effects of taunt.
Another option you could use is have another baton passer on your team such as Ninjask.
Baton Pass Ninjask (M) @Leftovers/ Mental Herb
Trait: Speed Boost
EV'S: 252 Speed, 252 HP, 4 Def
Baton Pass (Obviously)
Substitute (This is what your going to baton pass on to your Smeargle)
Agility (This is also what your going to baton pass to Smeargle to ensure your faster than your opponents)
Protect (To get a free Speed Boost turn and ensure your substitute is maintained.
The strategy is simple send out Ninjask at the start of a battle or when you have an opening. Use Protect so you get a free Speed Boost up. With Ninjask's 160 base speed and after one Speed Boost you will be able to out speed any Choice Scarf user. Then use Substitute and then Agility on the next turn if you still have your Substitute. After that you can either set up another Agility or use Baton Pass.
If all goes to plan when you baton pass to Smeargle it should have a Substitute and a +2 Speed Boost at the very least thanks to Agility.
Hope you find this strategy interesting :)