The brass tip is the nozzle, be gentle with it.
The best way i've found is to get some restorer (by Createx and usable across all variants of createx and autoborne)
get a small glass jar and put some restorer in it, pop the nozzle in it and make sure all the air is out, move it with a cocktail stick if you have an air bubble. leave it for an hour, remove carefully and use a long bristled artist brush and work the inside of the nozzle to dislodge anything stubborn.
flush with water, reassemble the brush and give it a rinse through with some water. if you have a dark surface behind the airbrush when you spray the water you will be able to tell if its spraying properly, it should be a nice conical shape, no spitting/spluttering, if not, soak the nozzle again, make sure the needle and aircap are also spotless.
I've never needed to seal the nozzle thread, just dont overtighten it and strip the threads when you do it up. It doesnt need to be super tight, just airtight
You'll get less blockages as you get better at appropriate reductions.
like i said, all part of the initiation