Doing exhaust work this weekend...

Does anyone know the size of the nuts and bolts needed for the following
connections...?

Collector pipes to Y-fitting
Y-fitting to J-pipe
J-pipe to cat

Too, any tip on cleaning the mating surfaces?  Just use a wire brush?  Or
get one of those wire drill wheels?

Thanks for the help!

Alan Bosch
& Phred ('88 Wolfsburg)