Can I control how my channel partners use MDF?

Unconditionally yes. You’re an investor giving them capital to effectively promote sales of your products and their services. Beyond having every right, you have a responsibility to stakeholders to monitor what is done with your investments. Partners with excellent marketing teams will gladly share strategies with you. Others will need your support to effectively use those funds. If they refuse your help, you shouldn’t offer MDF. Consider basing MDF on proposals submitted by partners complete with budgets and anticipated ROI. MDF should not be considered an uncoditional right of partners. It’s an investment. Require a business plan, and a marketing plan.