It really depends on the ambient conditions, as the sensors measure a change in electricity when you touch the wheel. On humid days or if you are sweating a lot, the conductivity is higher and less touch is needed to trigger the sensor. So some days a light touch with two fingers is enough, other days you have to grip a little harder or use a larger surface area (more fingers on the wheel). Most days, if I just keep both hands on the wheel, I will never see the warning.
In any case, touching the wheel should be enough. If you have to tug the wheel, then I think you are missing some
coding?