Section 6. The forester may demonstrate to owners of woodland, at a fee not to exceed the actual cost of the service, the proper methods of planting, weeding, selective cutting, pruning, thinning and other silvicultural practices for the establishment, improvement or regeneration of the forests. In connection with the distribution of trees under section nine, and in the distribution of trees for reforestation in water supply lands, town forests and other publicly-owned areas, the forester may withhold sale or distribution thereof until the land to be planted has been examined by him or his agent and approved for such planting. He may co-operate with the federal government in carrying out the purposes of this section and may accept on behalf of the commonwealth, and expend for such purposes, such federal funds as may be made available therefor. He may employ temporarily such technical foresters as he deems necessary to discharge his duties under this section and the employment of such persons shall not be subject to chapter thirty-one.