It always help for any control surface, as long as it does not interfere with the full deflection of the control surfaces.

At high AOA, there is a difference of pressures between both sides.
Any open gap allows a flow of air from the high pressure side to the low pressure side.
The main flow of air on the low pressure side is disturbed by this stream of leaking air that is flowing in a direction that is perpendicular to it.
That disturbance creates or increase turbulence that reduces the control action of the low pressure side of the control surface.

At low AOA's the problem is not that relevant.

I have used the 3m transparent vinyl tape mentioned by rmh, which has shown resistance to glow fuel of months.