Hey guys... let me begin by saying this is my first venture into the world of bass I'm normally a rhythm guitarist) and im looking for a little advice.

Ive just aquired a Tokai Thunderbird in a great deal and was wondering if you guys had any tips on how to get a good growl/rumble from it and if possible keep a nice punchy attack.

The bass feels really nice to play but I've not been able to play it through a bass amp yet.

As I will mostly be playing rock and metal I'll be using a pick, which I assume would help keep the attack tight, and playing through a friends Ashdown MAG 300H EVOII head with 1x15 and 2x12.

Im specifically looking for advice on eq, compression, overdrive etc. rather than replacing pickups and altering the bass itself.

Thanks for taking the time to read this and I look forward to your replies.
I'm not too sure about the growly tone but I'd like to contribute some things.

The thunderbird is generally not a tonally diverse bass, it is very easy to get lost in mud with the tone. It will probably take a lot of work to get a pleasing growly tone with good attack. Generally for growl you should boost the low mids on your EQ and cut the high mids, and play with the bridge pickup boosted, with your attack position close to the bridge.

Also, don't knock playing fingerstyle just because its rock and metal, you can get great sounds from fingerstyle in heavy music and I'd recommend practicing both picking and fingerstyle.
If music was the food of love I'd be a fat romantic slob.
Sorry if it seemed I was "knocking" fingerstyle, that was not my intention. Im sure at some point I will start working on fingerstyle but for now I think I'll stick to my picks.

Thanks for your input on the EQ. I've got a graphic EQ pedal laying around so I'll set to work with that.

If the bass itself is too muddy I may upgrade the pickups at a later date. I dont think it would be worth it yet though.
A pickup swap won't help the mud much...it comes mainly from the placement of the neck pup, and using to much of it. Just favor the bridge pup on it and you should be ok.
Nope, no sig here.
on overdrive, i just picked up a Ibanez Phat-Hed overdrive/distortion pedal and it's defenatly delivering alot of 'punch', but that is also helped out by my rig.