I solely prepared with the CBTs provided by them.
The actual test is very very similar to these training programs and so they are in my opinion the best form of preparation because you will not be surprised at all when.
For me and most of the other candidates who were successful it was not necessary to use any third party training software
I passed the DLR twice once for LH Italia and I prepared only using the cbt they sent me.
If you practice a lot that should be enough!
Good luck.