Bushwalk Australia

I am familiar with nikwax for leather but not the othe rproducts.
I want to waterproof a cotton drill cap, so nikwax for cotton I guess.

Some questions first:

Is for cotton the best product?
Is it really absolutely necessary to use tech wash first as that seems a little pricy per wash?
What is the best, cost effective way or product to wash waterproofed items?

Please suggest, reasonably priced online sources in Aus that carry a good range so I can order every thing in one go to keep postage costs down?


Regards,
Ken