Whats the best way to drive these in the rain/snow because they seem just wheel spin all the time force selector is at 100 %
Lower the force selector to about 60%. Once rolling, you can try increasing it until the wheels start slipping again.
Not directly. All it does is control your tractive effort (left gauge in the cab). Just think of it as the throttle. You need to use little throttle in adverse conditions to start without slipping and might need to open the throttle up again at speed to keep accelerating.
And drop plenty of sand. Fairly certain locos in TSW have an unlimited supply so just use as freely as you need.
