Cleaning out steam pipes.

I was wondering if there is anything I can do in preparation of a new steam boiler.

Presently, we had the 90 year old coal boiler removed.  It is a single pipe system.  They cut the return pipe at the lowest point and I noticed a lot of sludge inside the pipe.   They will probably have to remove more of the return pipe to correctly install a new boiler.  But I wondered if I should flush out the pipes from the radiators down to the return.   Not sure if it would be effective or not.  But I would rather clean them out now before a new boiler is installed.   Or am I imagining a problem that probably doesnt exist?