The long tail cast on and thumb cast on gives the same look but the yarn is held differently. So any advice I have given for the long tail cast on also applies to the thumb cast on.
When you do the long tail cast on, the first row is a wrong side row. If you use the long tail cast on, cast on a few stitches and start knitting the first row. Look at the knots at the bottom of the first row of stitches (see second photo below).
When you start knitting the second row, look at how much neater the cast on edge looks (see top photo below).