how do you trear rooms to bring up the null points

Any treatments applied near boundaries to reduce peaks due to room modes will also raise nulls because they are both fed from the same energy source. There are tuned absorbers which you can read about at
www.realtraps.com
http://www.quietconcepts.com/products-atp.htm
http://www.rpginc.com/residential/cinemusic-products.htm

OTOH, they are rarely needed as broad-band bass traps placed at boundaries (in the pressure zone) are cheaper and can be effective.

It is hard to treat the listening position(!) but you might be able to relocate it.

Kal

Well, there are alternatives:
1)Learn to use measurement and analysis tools.
2)Hire someone who can do it for you.

Kal