Supressive fire from other units is a must to my opinion. Smoke helps but is not the only answer.
Most of all I would try to supress with area fire the opponent. Area fire form other troops not advancing (1st squad advances, 2nd fires not moving), MGs area fire as well to suppress, artillery is ok but needs time and does not offer much vs a well trenched position in woods.
PS. In case you can spare some tanks even better to suppress with area fire.