Replying to a couple of different posts at once:
Yes, there's a danger that acetone and toluene/xylene will dissolve some plastics, but as Ketturi says, the plastic packages on most board components seem to be resilient. Individual results, as they say, will vary.
Windshield washer fluid is often a mix of water and methanol, so it will have some cleaning ability. In my opinion, it's not ghetto if it works-- just clever. I would still prefer to buy straight methanol or methanol/ethanol at the hardware store, but that's because I have one close by and the chemicals are readily available.
Some of the traditional contact cleaners have been reformulated, banned, or increased in price due to regulations on the ingredients that make them up. Luckily, methanol/ethanol/IPA are still inexpensive and readily available (at least here), and they're usually sufficient for washing down circuit boards.
If you want to use something more aggressive, I would try a commercial aerosol brake cleaner first. If there's an MSDS for it (there will be if it's sold in the US, not sure about international regulations), read it first to see (approximately) what's in it. Non-chlorinated ones tend to be a flammable mixture of hydrocarbons of some type. Chlorinated ones (non-flammable, usually) are something else entirely. A quick scan of an MSDS states that tetrachloroethylene and/or perchloroethylene are the ingredients in the chlorinated ones. I have no idea about their composition or compatibility with plastics or their suitability as a contact/circuit board cleaner. I tend to use the non-chlorinated variety out of personal preference. The only reason I mix my own is because I tend to do a lot of mechanical work and when I do I go through a lot of brake cleaner. It makes sense for me to buy in bulk, but maybe not for you.
Having said all that, whatever type of alcohol (methanol, ethanol, or IPA) you have available to you should remove most of the contamination with little to no residue. Only use something more aggressive if you really need to.