I didn't know about the baby oil or PB trick, but I have heard that conditioner will help a little. Just don't let her get wet when you know that she has them, this only tightens them more.
If the mats are big, then you are most likely going to have to cut the fur a little, there are mat shredders that you can buy (they look like tiny rakes but with knives) and that helps cut it up a bit.
Like Ann said the best solution for you is to get rid of those plants at the roots. I know what you go through though, we have a few of them around here too.
Have you considered having your Cocker's fur cut back a bit? Having short fur (not shaved) will make this considerably easier for you!
I think I posted a little bit about this topic, here's a link if you want to take a quick peek: http://k9academy.dogboard.net/dog-grooming-f9/how-to-get-rid-of-mats-t284.htm
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