I got it all clear finally, took about 45 mins till I was happy and sure.
First is just shook it dry till my arms hurt.
Then I dropped magnets down the cap attached to string so (so I could pull them out again), they just stuck the the inside of the tunnel, poured petrol in and shook it loads. Did this about 3 times, each time pouring the petrol out (loads of alli and plastic fillings came out), the pulled the magnets up and cleaned off the steel bits.
Came out all well and today I'm spraying it.
Cheers all,
Mackenzie