My younger brother and his friend went till umbrella waterfall, though its not nathigali, but you can easily go there without any issues insha Allah.
In September I've seen people on their CD70 in SaifulMulook, compared to that, nathigali is walk in the park.
Also, as mentioned above, have some ideas by watching YTube videos. Plenty of videos on the subject and do's and don'ts.
Best of luck, safe travels, enjoy North of beautiful PK!