I had a 390 single engine, which is close to the 40. Most of the 40's I delivered had twins.
When I took my 390 out for the first time, I went out into the bay on a calm day and started backing up at various RPM's to get the feel of the prop walk. I found that at idle speed the prop walk was minimal, so I always did my best not to power up when docking. I did have a bow thruster, which I used more for minimal adjustment (sometimes just to change the angle as conditions changed).
Try mastering backing without thrusters. After that, I say if it's on the boat and can beneficial, then use them, but as an aid.
Enjoy!