Tracking hours for freelance designer, by month

I cannot be the only person who needs to do this… I manage several freelance designers who have retainers for X number of hours per month. We have projects spread over several boards. I need to be able to see how many ESTIMATED hours we have dedicated to each project and then how many ACTUAL hours have been used each month.
On each board, we have a column for estimated and actual hours and we’ve been diligently using those. The problem is, I need to see a high-level projection for each month of the estimated hours for each designer.
I have attempted to make a chart on our dashboard, but cannot filter by dates and designer.
Any suggestions?