So I have got my nuke done but now

So I got my nuke done thanks to Mindthemoods

but now I need my mushroom cloud. So I thought maybe a block bench block model would work that would place the block after the crater was made but it won't let me get it that big so I though maybe particles so I made a particle but it needs to be bigger and it moves around anyway once I made it size 48 it did not show at all? So now im left without a mushroom cloud effect if theres any ideas please state what and how to do them in the comments