Hey guys!

Im looking for help because there is this art contest that i want to participate in, but, i need to make a poster 90X60 cms and i have this issues:

1.-Due to the size of the image to print my poster, do i need to make it 300 dpi?
Cause normally 300 dpi works great when im looking at it very closely like a magazine or book, but for a poster this big can i print it with less dpis or does it really need 300 dpi to look cool? Or is it just ok 200dpi or 150dpi on 90X60 cms?

2.- Its enormous and making a single stroke on my wacom tablet on photoshop cs6 is just a nightmare, its sooo slow (even if i adjunst the brush spacing)!!!
So making a digital painting is not an option at this size and resolution!

What can i do?!

Thanks for your time!