How to create a quote request form?
Entity Forms are, IMO, a long shot. 

1. Webform module

You can use Webform module, and add an Option list (HTML select list) field to the webform, and autopopulate it with a URL parameter. Webform module supports populating the field value automatically from any $_GET, $_COOKIE, or $_SERVER value. 

For the select list values, you can use a View to build the list of Product nodes. 

2.  Entity Forms

Since you already have an Entity Form, you can do it with the traditional field approach. 
Similar to the webform's select lists, you can create a View to list all Product nodes. Entity Reference module supports Option (radio, select, checkboxes) field type, with the options fetched from a View. You can use Entity Reference Prepopulate module to populate the Product node from a URL parameter. 

3.  Custom module

Either way above, you will have to use some modules. If you are OK to create a custom module, you can do it with a little coding as well. Be prepared to go through a little bit learning and conventions first. This is a nice guide to get you started. 

You can do this easily with an EntityFieldQuery to fetch the eligible nodes list, and then setting the #default_value in hook_form_alter hook.