Are you talking about Fast Hand/Juggle stuff? If so, you need to bear in mind that these transitions come out of being completely comfortable with the tricks as isolated moves (1-Turn Lighthouse, for example), and move into a combination.
One example might be Swing-In (Juggle) > Lighthouse (damn, should have read the definiton article in Tricks more closely). You're essentially executing a 1-Turn in Ken grip, but thinking about it like that won't help; try a normal Swing-In and put some flip into the Ken, reach for the tama. Do it again. And again. Just concentrate on getting the spin right. If you have practised 1-Turn Lighthouse enough you will begin to adjust the tama catch by muscle memory, so to speak.
Technically, then, you're only challenged with the Juggle - that which makes these Trade-Spike/Juggle/Fast Hand tricks look so daunting is that the practise polishes away the split, like a seamless bit of editing, but don't let yourself be put off by this, it's just technique and (as aforementioned) practise, and occasionally breaking down the game a bit. Your Thumb-Trap > Aeroplane-In in Tricks is an example of exactly this!