Put a Wynn 1 micron drum filter on your HF unit. It can exhaust in the same room. Wear a mask (HF sells surgical style masks that are very comfortable for about 10cents each. Get a WEN room filtration unit (was 90 bucks at WalMart, delivered locally). Fiddling with DC home made stuff will eat money you could have used to get the Wynn and WEN units.
Also, take some tape (There is a non adhesive, stretchy tape), and tape around the top of the plastic bag on the HF unit. Mine leaks sawdust like mad without the tape. Hint, clean the metal at the top of the bag first.
I wasted hundreds of dollars on home made solutions to DC, and wish I'd just done the HF unit right in the first place. Now, if you go into my shop, the dust level is far less, but I will ask you to put on one of those disposable masks. I'm a throat cancer survivor, and sawdust is a trigger for that disease. Take it seriously is my suggestion.
The more I do, the less I accomplish.