Good advice above re wiring in series to slow things down. The only issue there is that if one truck loses traction it will spin up fast while the other one stops. You lose the "limited slip diff" kind of effect of having the motors wired in parallel. But worth the trade-off for me.
I have been experimenting to try and get the smoothest starting off and slow running on DCC. My observation is that the motors are the weakest link. There's a lot of end float in the motor shafts so when you first apply power, instead of the loco creeping forward, one or both of the motor shafts will climb up or pull down inside the motor and take up the slack before the loco jerks forward. And the motors seems to vary quite a bit so it's hard for the decoder back-EMF to manage the different loads.
The closest I've come to good starting and low running is by removing one motor. But you lose a lot of tractive effort this way so probably not worth it unless you run consists and don't have grades. Here's a clip of today's experiment with a single motor, I took the motor out of the front truck so it can free wheel. It's a Loksound Select HO with as much fine-tuning as I can do. You can hear how the decoder tries to manage the variable load of the cheap motor. I did try removing the flywheel which usually helps with starting off, but the slow running is worse as these motors cog badly without the flywheel.
Here's a clip of a 3-unit consist all still with both motors in and Tsunami 1 decoders. Not such good starting and slow running control, but probably OK for mainline and long trains.
And for contrast, here's a clip showing the almost imperceptible starting off achievable with single motor drives without flywheels but with good quality decoders. The P&D F Unit has Pittman and Loksound Select L, the Red Caboose GP9 has a Maxon coreless motor and a Loksound Select HO decoder. Both have Finescale360 driveline upgrades. However, at any speeds higher than this, they shake, rattle and roll because of the chain drive. So I have a major upgrade coming from Jay C which will finally deliver the performance I want under all condtions. 
HTH
Pete
