Ballasting track, while tedious, need not be daunting. Your local hardware store (or even big box stores) carry a product called "polymeric sand" which is designed for use in patio paver joint applications. The cool thing is that the product (or any similar with different brand names) has adhesive blended with O scale sized ballast (sand). Oh, and polymeric sand is cheap--$20-25 per 80 # bag, so you can share with rail friends.
Simply apply the sand/ballast, spray with water, and you're done. Start with dry track, build your contours and have FUN. Photos attached are part of a 90-car division point yard on my railroad. I'm just beginning to add scrap, pools of water, weeds, etc.
Don
