Out of all my years of experience I can honestly tell you there are NO tips and NO tricks to smooth a coaster well. Sure theres the elementary for the maths guys and for the people who have tried that and failed your best bet is to download Busters track smoother and see what you can do with that. It's really a good tool and under estimated if you use it well that is. If you purchased the construction kit, you can use the radius comb and smoother in that too. That will give you a good idea as you can see where your pumping occurs and what not.
Regards.