M105 can dust on occasion depending on a number of factors such as the amount used, the type of pad, the specific paint, and any chemicals that are present on the paint.
Dust is a combination of the abrasives (many of which are heavier because they are coated in abraded paint), abraded paint residue (APR), and abrasives that have clumped together as the lubricants have dried up. If you have chemicals (trace residues of detail spray, clay lubes, waxes, polishes, car soaps) then this can accelerate the clumping which then will increase the dusting.
To reduce dusting I would make sure the paint is as free of chemicals as possible. This is why I personally like to wipe the surface with CarPro Eraser prior to polishing.
Also clean the pad thoroughly after priming and add three small drops of product after.
Past that, I don't mind the dust. As mentioned above, it is really the "waste" product that is being ejected which keeps the pad/polishing surface "clean". You can use liquids, such as detail sprays to prevent the dusting from occurring, but this recycles the the clumped abrasives back into the polishing process which will negatively effect the finish quality.
Ultimately it is your choice. If dusting is a concern you can try Meguiar's D300, mix D300 and M105, or use different products. I plan on washing the cars I polish anyways, so I will welcome any dusting in exchange for getting the best performance out of the product.
