James; on the low-pass I would roll the Q all the way off and then work with the frequency setting and volume of the filter.  You can always add Q to taste later, once you have the frequency dialed in.  Also the position of the bass setting of your amp will have a significant effect on the filter.

It has been som etime that I used mine but I recall I most of the time work in band pass to wrk in certain frequencies!
Amazing little box indeed!
I only discovered 1/10th of it!
 
PTBO

So...Saturday night I used one channel as band pass and one as low pass and had amazing results.
 
I couldn't have been happier with the way my guitar sounded.
 
Thanks everyone for your help and input.