Tweaks such as demagnetizers ionizers for lp's

What about this one on eBay? Search for 360166354150 (item listing number).

Can you use non-powered magnetizers / demags with similar results to the powered ones or do they not keep up?

The Talisman demagnetizer from Walker Audio works very well for CDs and interconnects. It is a relatively small passive device and IIRC contains rare Earth magnets oriented in at least two planes. There is a great deal on Audiogon for a previously owned Talisman as we speak.