Disclaimer: this works for me but it might not be recommended by all glove companies. Sometimes this makes dye come out, sort of like when you're caught in a storm and your hands turn red or blue.
I want the salts and other sweaty stuff out of the leather so I wash the gloves before I preserve them. Do one glove at a time. Fill it up with cool water at the sink and then close-off the glove gauntlet with one hand while the other hand gently squeezes the glove so pressure forces the water through the leather. Repeat a few times. Now you have the leather wet and saturated.
Then add a small capful of very mild soap (Woolite) to the inside of the glove, fill with water, shake it up, and repeat the above procedure. The soapy solution will work its way through the leather. When it's coming through, stop and use your fingers to massage all the dirty areas. Add a little more Woolite on the outside surfaces and massage. Do not use a brush because you can damage the leather. Use your fingers and let time work for you. Force some of the soapy solution through the leather to get all the crap out of the leather. You'll be surprised how much dirt comes out!
When they're absolutely clean, rinse and rinse and rinse until there's nothing but clean water moving through the leather. Force clean water through the leather to force the soap out.
Do the other glove. Then lay the gloves on a towel and allow to naturally dry for a day or two.
When they're completely dry they'll be clean and hard. That's when you apply a leather conditioner to the entire glove. Take your time and don't use too much.
You'll end up with clean, preserved glove. I do this once or twice a year and so far my gloves have lasted for years and years.
I seem to remember a deerskin glove company called Thurlow recommending this procedure. Works for me.
