Usually if you soak in some type of soft cleaning solution you should be good. Just vigorously pump the siphon after it has been sitting in cleaning solution for a while. You shouldn't have too much gunk in there assuming you clean right away, that might be the best advice. After you use something get it soaking right away. PBW is a cleaning solution that is very effective if you let things sit overnight.
Scratches in plastic are trouble. It is probably not worth the risk using that again. Next time use soft clothes.
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