I used to be a senior consultant at SKP before I moved to MBB.
The process here depends a bit on the office but usually goes as following:
1. Math test online (very different from MBB exams - this is purely a math exam)
2. phone interview (classic case interview)
3. phone interview (classic case interview)
4. Recruiting day (up to 4 interviews and a math test)
I wouldnt say there is a particular different way to prepare for SKP interviews, just know the company well, study pricing cases and make sure usual key areas are covered.