To clean I would suggest something like Autoglym interior cleaner but to dress (or very mild cleaner) my favourite is Poorboys Natural Look which gives a loss gloss finish
As for the late 156 interior, you can buy special pads but I use a soft dish washing pad which works almost as well as the specialist products. The key with any dressing is to apply a small amount, let it dwell for about a minute and then buff. Too much product or not enough buffing will lead to steaks and a poor finish. A dressing will always look better on a cleaned surface
It is easy to get caught up in specific brands but I would say technique and process are far more important.