Well developing routines depends a lot on the DJ and his style.
As you can see the SX and TM demos in those videos are both really good, but totally different in style. DJ Angelo is a great guy and one of the best in making really lively scratch demos. Hence his whole demo is focused around scratching. The SX demo is much more trigger pad focused.
Now every DJ goes differently when doing such routines. Some have a toolset of simple routines (different scratches, prepared sampler sounds,…) that they simply add together to make a routine.
Really important about the routine is song selection. You need a song that will cater to your routine, but also be spicy. For example Angelo picking Praise you and add his own voiceovers is ingenious and works much better than to simply take a hip hop beat and scratch over it.
The most important thing however is experience and knowledge. You will not see many new DJs perform such routines as they lack the skills needed and the experience to know what they can do. If you do it on video it is a bit more easy as you can simply take another go at it, but when performing such routines live you need to be in your comfort zone of knowing what you can pull off.
Beatjuggling and scratching are generally 2 skills most needed at least in some extend, even if it is only to be more confident in your skills.
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