I am new to this so by no means an expert, but I find that I can lather fine without seeming to waste soap (I can detect only a very slight depression in the soap cake I have been using daily for 3 weeks). I am using a Col. Conk's almond soap, and the $30 silvertip Chinese brush off eBay.

My method is soak the brush in hot water, leaving the soap dry. Give the brush a single slight shake to get true excess water off, swirl the brush on the soap for 15 seconds or so, then build lather on my face. To re-lather, I just use the brush on my face to build it up again, no extra water soap etc. When I am done shaving, I use a tissue to pat dry the top of the soap. I do have soft water, which makes some sort of difference I'm sure. At least with how I do this, the amount of water on the brush makes all the difference for lather that lasts or doesn't.

So - no advice for your method problem, but perhaps this is another method to try if you are trying to extend soap lifetime.