I strongly recommend Videos by Paul Scoles for beginnners as well as advanced modelers. Paul shows and explains "how-to" do scenery on his Sn3 layout. His explanations of tree making as well as completing the minute details of total ground cover will give anyone the confidence that "I can do that"! I have several other videos, but if I had to chose one (especially for beginners), it would be his "Advanced Techniques for Realistic Scenery".
Dave G.