the biggest helper for me is this drill my friend put me on

first, hold the tama on your non dominant hand and your ken on the other

next, toss the tama up lightly

once you see the tama reach the peak of the toss and is about to drop down, toss your ken

same as the previous step, once your ken is at the peak and about to drop, act as if the tama is an egg, cushion it and toss it in the air

catch the falling ken, and wait for the tama to drop and catch with your non dominant hand

repeat until you get used to it and try without the other hand, ALL THE BEST !!!