Dear Tom, use a lens which has a wide aperture for it's size, ie; 300mm f5.6 lens for 10x8 film, or 50mm f 1.4 lens for 35mm.
My personal favourite is the legendary Kodak Aero Ektar 7inch f2.5 lens on 5x4 format. If you can't get hold of one of those, try the 105mm f 2.5 standard lens on a Pentax 6x7.
Regards, Andrew.