We would recommend only using the Bellow Hand Duster as is, and not attempting add any additional tubing to the end of the extension. You most likely would lose both dust and necessary air pressure out of the connection. If you need to reach longer distances, you could something like the B&G 2 Quart Duster 1152-A, which has several different attachments and adds an electrostatic charge to insecticide dusts. You may browse all of our Dusters here.
The Bellow Hand Duster will work well with any dust. We highly suggest you read over our detailed article called "How to Get Rid of Ants." This gives a detailed breakdown of what steps to take for treating whether using baits or sprays and where to look for nesting sites. Boric acid dusts can be used but they can take up to 14 days to kill an insect after they ingest it so might not be the best solo item to use, depending on your situation.
We would recommend filling the Bellow Hand Duster only 2/3 full, as well as adding some small pebbles or coins to prevent clumping. Use with the cap facing the ground and gently puff the dust. The included cleaning tool can be used in the extension to clear a path for the dust to disperse. We also suggest using only fine insecticide dust through this applicator. Please call us at 866-581-7378 if you need further assistance.
Insecticide dusts should be applied with a hand duster, such as the Bellow Hand Duster. This makes it easier to apply the product in cracks and crevices where insects are found.
The Bellow Hand Duster and the Long Shot Puffer Duster are designed to treat cracks and crevices or voids where you place the tip of the duster, so it will only travel a few inches from the tip. If you have a tall vertical void to treat, you could also drill high in the column and let gravity carry the dust down.
You could potentially use a bellow hand duster to apply a dust such as CimeXa Dust to carpets before working the dust into it to treat for fleas. We do not, however, recommend that a dust be the only product you use for flea control. Our Indoor Flea Kit contains a dust plus a ready-to-use spray which has quicker knockdown of adult fleas plus and Insect Growth Regulator (IGR) for long-term treatment. Please take a few moments to review our Flea Treatment Guide for more tips on how to eradicate this pest successfully.