In my experience there are 'trouble spots' that will always be more difficult to get bbs. In my case the same spots tend to be the ones that need a bit more attention to get totally smooth to the touch. Some of these I've figured out and they no longer need any extra attention. Other spots, all on the neck/jawline , are still difficult to 'get' on the first or second pass. If I feel like it I do a water pass on those and if not I call it good enough. BTW, doesn't matter if I'm shaving with a straight or a Merkur slant with a Feather, the same areas are tougher that the rest.