there's loads of info in this thread and all about mate, it doesn't hurt to do a bit of research yourself.
Using a tshirt completely depends on the individual shirt, some can be fine others can let through enough paracetamol to damage your liver. amnesiaseizures method is a bit excessive, no point doing it twice through a tshirt. The method using 3 sheets thick of kitchen roll in the top of a 2l bottle as detailed a few times in this thread and countless times elsewhere is the most successful method I have found. If unsure about the safety of your final product then you can leave it sitting in the fridge for a few hours and any remaining paracetamol will sink to the bottom.