Ive been to a few of those shops in the middle and outer Sydney rings over the years. Talking about NHJ, it is mostly miss but sometimes a big hit. The success rate is similar in the city I reckon although with more establishments to choose from. My experience is that every establishment has a culture which is cultivated by the mamasan or other MLs working there. When you find a place where the culture is accommodating and relaxed it seems to apply to all of the girls. I think the ones that don't like it tend to leave. So when you find a place with the right culture then it pays to stick to it. You can still get a lemon at one of those places but when you strike gold then there is the option of a repeat visit and possibly cultivating a regular. It really is lucky dip and the expensive part is having to pay for so many 'meh' massages before you get a good one. No way around it. You also have the chance of scoring a naive and horny newbie (although this is harder these days) or sadly, you can get one that was once good but has become jaded (or just having a bad day).

Reviews can help. But although many contributors on this forum are generous, I think that sometimes when a punter finds a diamond in the rough they are reluctant to share the info. I am probably guilty of this. However you can sometimes get a sense of where the more accommodating shops are by joining the dots between reviews. My problem is I am looking for fairly clean experiences but sometimes places can be so risky and dirty (offer of BBFS off the mark etc) and this makes me uneasy despite the thrill. I tend not to go back to those places.

Don't overthink it. Set a budget. Spend the money and the time. Explore. Write some reviews...