First I started by sanding the back of the domino
Then I apply gesso to the sanded domino applying layers which I sand
making it smooth
Then I draw my design. Some use felt pens, some paint
since I was experimenting I tried using Micron Pens they worked great!
Once I am done and satisfy then I sealed mine with Diamond Glaze.
And, others use other sealers too, you just have to experiment, see
what works for you.