Cleaning New Steam Boiler

I am interviewing contractors for replacing a one-pipe steam boiler. As per Dan's book, I have been asking contractors whether they will clean the boiler following the manufacturer's guidelines. I've seen that both Weil McLain's and Burnham's website have instructions on how to clean the oil from the new boiler and piping using chemical compounds (trisodium phosphate or other compounds) in the boiler.

Most of the contractors I've been interviewing dismiss the notion of cleaning the boiler per mfr instuctions as part of the installation. They propose to "do nothing", "run the boiler at high pressure and drain sediment and oil from the mud leg valve" or "install a skim tap and skim the oil of the new boiler from the surface of the boiler water. One contractor has suggested that using these chemicals to skim the oil from the boiler will damage the pipes, cause existing piping dirt to get into the boiler further causing banging in the pipes (which we don't have now) and creating leaks in the pipes (by clearing away dry sediment that may be plugging a leak now(?)). Are they right? Are any of these other methods of skimming the oil effective or should I insist the contractor I pick follows mfr guidelines to the letter?

Only one contractor agrees to follow the manufacturer guidelines for cleaning as the proper thing to do, but that contractor has given me suspect answers in other areas of installation.

Also the contractors I have been interviewing have offered the Burnham Independence, the Weil McLain EG series, and a Crown boiler (he views Crown as having newer technology--but hasn't give me a model number yet). Any intrinsic reason to prefer one of these over the other?

Thanks in advance,

Jae So