Hello and welcome to YT! I am sure that you are very frustrated with marking and the issues that you are dealing with with your newly rescued little Yorkie. I can give you several suggestions on how to get things under control. First off, you need to purchase belly bands for both of your boys. They are marking because of territory and it will continue unless you belly band and clean anywhere they have marked with a good enzymatic cleaner like Nature's Miracle.
Here is an article that might be helpful in training. It's titled Puppymill rescue but it will apply to just about any rehomed dog.
http://www.yorkietalk.com/forums/tra...nt-advice.html
My next suggestion for belly bands would be to purchase several bellybands and keep them on all the time unless you are outdoors.
Here are a YT vendors to look at:
Washable Belly Bands by T. Bumpkins & Co. and Doggie Pee Pads
Good luck and if you need anything else please just ask. I want to help