If a spotter appears on Floor or Pommel/Mushroom, it’s a 0.5 point deduction (without any contact with the gymnast). If there is an active spot (on any event), then you loose an additional 1.0 point. If the judge determines that the gymnast could not have completed the skill on his own, the skill won’t be recognized, another -1.0. All execution deductions apply as well.
So, a coach who grabs & flips a gymnast in their Floor BHS skill would have a -0.5 + -1.0 + -1.0 = -2.5 from the final score, before any other deductions come into play (ie, flexed feet, bent knees, angle & hold deductions, and extras hops/steps.