I noticed small patches of rust under the grips and more on the frame under the beavertail grip. What grade of stainless do they use? Is it stronger than %100 stainless?
It's obvious there is some regular steel in the mix.
If you use steel wool , make sure it is stainless steel wool . The regular steel wool can leaves particles embedded in the stainless allowing rust to keep coming back .
My recommendation :
Most of the cleaning kit companies market a stainless steel tooth brush . Also , 3M Scotch Brite pads . These items have worked well in our shop for many years . Use plenty of oil and gently scrub making sure to follow the grain of the metal . It should clean it up .