8 years flying the A320 and we did single eng taxi in on a regular basis. Let the engines cool for 3 mins then when you are going straight with no brake being applied Eng 2 off. All of this is tempered with a degree of airmanship. If it is raining or snowing it is not a good idea. The SE taxi out was also recommended if you were light and it was a long taxi out but it was rarely done. All of this was done without the APU and only once did I hear of someone having a problem. New procedures now call for the APU to be started and this seems to add to the workload and consequently fewer SE taxis are being done. On the A340 we shut down number 3 almost all the time on the taxi in and if you are really light, start the APU and shut down 2 and 3. The A330 also taxis well on one but again you have to be light. After saying all of this nose wheel scrubbing is a non issue with some planning.