are you trying to model the head or just a flat face type mask?
i have never really liked modeling with splines, i find that starting with a box and cutting is the best way to get what you want.
http://www.enriconencini.com/tutorials/part1/index.htm this is a spline modeling tutorial, read through it and see if any of it applys to what you are trying to do.
with the spline also, i think that you have to deselect create new line which is above the spline creations and use snap as well, but I have never modeled with splines so i may be of little help to you.
hope this helps