I am renovating an old building that has 25 ft, 2x12 rough sawn joists exposed. I removed old mildewed ceiling tile, cleared out old insulation and am going to leave all the joists exposed as I've got a new pitched roof with insulation on top of the old flat roof. This old timber is in great shape, despite lots of leakage over years of abandonment. I want to stain the beams with an opaque stain but there is a lot of dust clinging onto the beams. I've used a leaf blower and have started hand brushing but there seems to be no end to the dust that emerges as the grain is very deep. So I'm wondering if the right sealer, varnish, etc. might just glue the dust in place after I've stained ? If so, could anyone recommend a product or offer any other suggestions ? Thanks.