What size needle/tip for spraying cellulose?

Not sure if the set up is important but full details as below:

Compressor - 50l 2.5hp 9.6cfm

Paint - cellulose 50:50 (top coat)

Spray gun - TBC but probably a LVLP gravity fed, just not sure on the needle/nozzle/tip I need for cellulose

Thanks in advance

Matt