Schleichs are among the easiest models to repaint, so don't worry! I use pastels or acrylics, or a combination of the two. Acrylics are very easy to handle, quick-drying and don't require any special solvents. The ones from Games Workshop/Citadel are excellent for basecoating, being specifically made for painting models.
Pastels have to be the dry chalk kind, not oil pastels, and preferably high-quality soft ones like Sennelier. You don't "draw" on models with pastels, but grind them down and apply the powder with a qtip or paintbrush. The main advantage is the colors are easy to blend, create a smooth color with a lot of depth, and don't leave any brushstrokes - however, you'll need to seal with fixative between each layer and there's always a risk of fogging or sealant drip which is really hard to fix.