How do I set "Add to Cart form" css globally using Commerce Kickstart as basis?
My solution is not elegant, but it got the job done:


Using inspect element, identified css that dictating styling of the "Add to Cart" form elements that I wanted to keep. This css was buried in the subtheme_style.css file associated with "Product" only: .node-product-type. 
Copied css to start of subtheme_style.css file
Removed the references to .node-product-type. This set all the select widget fields and all the "Add to cart" buttons to the desired style/look. 


This seems like an odd way to go, but also means that I don't have to differentiate among all product display types, as I build out panel displays that are unique to each one. What would you have done differently?

This is the css that I repurposed and generalized by deleting the reference to .node-product-type:

.field-name-field-product form.commerce-add-to-cart label {
  float: left; 
  margin-right: 5px;
  width: 45%;}

.field-type-commerce-product-reference form.commerce-add-to-cart .form-submit {
      background-color: #9E4934; /*CG Add to Cart button*/
      background-image: url("../images/bg_add_to_cart.png");
      background-position: 90% 50%;
      /* LTR */
      background-repeat: no-repeat;
      border: 0;
      -moz-border-radius: 8px;
      -webkit-border-radius: 8px;
      -khtml-border-radius: 8px;
      border-radius: 8px;
      color: #ffffff;
      font-family: "Open Sans", sans-serif;
      font-size: 17px;
      font-weight: 400;
      float: right;
      margin-top: 40px;
      margin-left: 5px;
      /* LTR */
      padding: 5px 50px 5px 10px;
      /* LTR */ }

.field-type-commerce-product-reference form.commerce-add-to-cart .form-submit:hover {
        cursor: pointer; }