Fair enough. Here's why I ask:
Mottling is really difficult and I sure don't want to sound condencending because you are obviously a sharp guy and I think you can probably do any darned thing you put your mind to.
But I think you should take a little time to get the feel of airbrushing before you jump into mottling.
That said, here's a few ideas.....
Acrylics are harder to mottle with. The way you gotta do it makes dry tip worse. Tamiya might be a decent acrylic choice, though.
Someone is bound to say your .35mm needle is too big for mottling. I would like to disagree in advance.
I'd advise against setting the needle-stop. When mottling, you do it by feel. I've heard it said that needle-stops are useless when spraying acrylic due to the dry tip issue yet again, and becuase the stop keeps changing. I tend to agree.
If you really must mottle with acrylics, I've heard Gunze Aqueous can be a good choice. I've pulled it off with Vallejo once. Sadly, I'd given up drinking prior to that, which was, in hindsight, a mistake probably.
I'm going to shut up now. Take your time. Even after you've been airbrushing for years, I'll bet there'll be times you want to launch the thing out a window. I do. I hope you take your time and have fun.
Edit: just reviewed my post. I'm sorry, I didn't set out to write a ramble.