I need to do some 'piston' style, air release foley moves next week. They have to be clean (ie no erroneous rattles from the props!) so was just wandering if any of you guys had any good ideas! The best I've come up with so far is a can of compressed air and a metal pipe (I'd quite like to get some metal to it you see!), which is kind of ok but not quite right. I'd really like some options to work with so could do with some brain on this one! Thanks in advance....
I would try a variety of bicycle pumps. I used to have an old metal one that would make an awesome suction sound every time I used it. A balloon pump, such as the one below, can work well too. They usually have larger nozzles so offer a different type of air flow sound to a bicycle pump.
Try to record at 192KHz 24 Bit, allowing better results when playing with pitch.
To build on Iain's suggestion, also look into manual pump sprayers, available at most hardware/home improvement stores, the kind used to spray chemicals on plants. Their plungers are thick and sound pretty neat. Likewise, manual bilge pumps (of the kind sold to kayakers) are small, inexpensive, and also have a cool sound; Bilgemaster brand is probably the most interesting sounding.