Here's one of my simplest astro projects. I recently had to clean my scope optics and try to not have anything in contact with them if I can help it. I've heeded various warnings about canned air before and thought about adding a valve to an old can to make my own. On a trip to the local pound shop I saw a much easier solution.
This is a simple balloon pump which can easily give as much or as little air as required. The only drawback is that it needs two hands to operate it. Obviously care needs to be taken in use to keep the nozzle from hitting an optic. I imagine though that a brush or different attachments could be made to suit various purposes. I did take it apart when I bought it and thoroughly washed all the components to get rid of mould release agent etc. The tissue on the back acts as a crude filter on the intake so that dust and other particles don't get blasted onto my lenses. So far it seems to be working very well.