Pai An (slap press or slap desk) also known as Yan Qing Po Shou (Ying Qing’s Counter Hands) has many variations. Pai An Sao Tang is perhaps the most complex and demanding of these variations. Grandmaster Chiu Chuk Kai of Taiji Praying Mantis taught a version of Pai An, which is called Xiao Kaimen (little open door). It is very similar to most other PM styles' Pai An; furthermore, he taught an extra piece, Dai Kaimen (large open door). The Dai and the Xiao Kaimen can be practiced separately or link together as one form. It is believe that the Dai Kaimen is not widely practiced today in the Mantis community. The linking as a form doesn't mean that Pai An is a form per se. They are generally regarded as separate drills in CCK TCPM (TCPM for short) tradition. There are also 2 ways of doing the last kicking section of the Pai An in TCPM. One way is to perform 2 low kicks, which is relatively easy to master. The other way, Sao Tang, is done with 3 spectacular kicks namely, tan tui (front snap kick), siao tang (floor sweeping kick) and bai lin tui (lotus kick). This combination and it is counter found in this section illustrates the essential torso method of praying mantis kung fu.
The basic break down of the Pai An or Xiao Kaimen will show that there are about 3 different pieces of drills. The first part is a variation of Wei Gwa Shou (outer hanging punch). The second part is Zhan Nien (contact and stick). Finally, Sao Tang (Floor Sweeping), which is Shan Zhuan Teng Nuo body method. Wei Gwa Shou has a Fanche (waterwheel) quality to it and Zhan nien is obviously mantis sticking skills. Adding Sao Tang, it is pretty much mantis skills in a nutshell; therefore, IMHO Pai An has tremendous value in the PM system.
The last section of Pai An (Sao Tang) is indeed a kick combo. The counter side would do a different kick combo. The interesting thing is that both sides can take turns in drilling the 6 moves (3 for the advancing side and 3 for the retreating side) back and forth, over and over again. It is quite taxing even if it is only ten repetitions each round. So I would suggest doing five reps in the beginning and build up from there. This drill is basically the Shan Zhuan Teng Nuo (SZTN). It is not just about kicking. After drilling these moves flawlessly, we can then add in or rather break down the drill into applications (ie takedowns and/or escape) where SZTN are fully applied. That means we can see the full extend of SZTN in close quarter combat. BTW, multiple partners can be introduced if the escape scenario is desired. Also ground grappling techniques can be drilled together with takedown. This would be more of an individual choice of course.
Pai An in TCPM can also be done with 2 low kicks instead of the 3 kicks combo. In that case, the timing of the hands and legs becomes more important. So classical PM drill such as Pai An is rather versatile and loaded with good techniques.