I would certainly agree with GD, dust in the house is not a great idea. Chx are very susceptible to respiratory infections and dust can irritate their respiratory tract. Also dust is an effective vector of disease. One suspended dust particle can carry thousands of viruses which are easily breathed in. You can use DE effectively against Red Mite and reduce the dust problem risk by painting it on as a slurry.
Mix a surface disinfection concentration of Vanodine V18 disinfectant (as given on the bottle). Add DE powder mixing as you go (add powder to liquid) until you have a thin batter consistancy. Paint on all surfaces of the perches and in corners, nooks and crannies in the house and nestboxes after every 2 or three cleans (avoid washing off between deeper cleans). See
http://www.british-birds-in-aviculture.info/Vanodine.html for info on the benefits of this disinfectant for use on dirty surfaces.
I wouldn't advise you to use DE as a wormer or to dust on the birds see
http://www.shagbarkbantams.com/de.htm which is a bit more alarmist than I think is warrented however it's worth a read. For worming, as GD says, use Flubenvet which is safe and proven against a broad spectrum of worms.
"White powder or spray for RedMite". If this is the Barrier Red Mite treatment you should save your money as it's not effective. The active ingredient in these products is Citrodiol which is a mosquito repellant for use on people and is unproven (according to it's manufacturer) for Red Mite on chickens. Using the sray on the house is also not how Barrier recommends it is used (read the bottle). Red mite are not attracted to wooden houses they are attracted to chx and if it is going to be effective at all it needs to be sprayed on the birds (a completely impractical procedure for more than a few chx despite Barrier's claims it's used by commercial poultry keepers.) It's just expensive chicken deoderant.
The only effective (longer term and persisting effect) treatments are pesticides and the most effective of these are reserved for professional trade use by regulations. Red Mite are easy to kill, pretty much any detergent will do the job, however as others have observed they only work on contact and once dry they have no enduring effect so mite and eggs which have escaped the washing quickly recolonise the house. Steam cleaning works and DE used after a steam clean will deter further infestations. DE isn't effective at treating heavy established infestations but it does protect against new infestations and a valuable treatment which isn't subject to restrictive trade use.
HF