Question: What the best way to attach real hair to a kit?
A: Seal your work, then use a some Golden Fluid Matte Medium (Liquitex Matte Medium Gel will work well, too) on a brush for the glue. Apply it to where you want the hair, then gently push the hair into place and let it dry. The medium will dry flat and clear, and hold the hair w/out a problem. Once it’s dry you can trim the hair anyway you like.
Always work in rows( or layers for a better word), from the bottom up, this way the rows will cover the roots of the previous ones below them. it makes it almost impossible to see how its been attached.
Perhaps a little old now but still useful, a basic tutorial on attaching synthetic hair.
Useful article by Neil Marshall from Military Modelling magazine
Part 1 of a very useful article on the selection and preparation of hair for use on a model
Useful article on attaching hair to a doll