transmission flusher (BG, hotflusher.com)

[HuskyMan]

transmission shop quoted $850 plus possible additional costs if exhaust manifold bolts break during repair. they have a BG transmission flush machine (cost $4,000). they don't have much experience with mercedes but seem to be well versed in automatic transmission technology. I am ordering the transmission from Peter Schmid transmissions in California (for a 1991 merc 560SEL). Indy with very good reputation priced the job at $900 FLAT RATE. HOWEVER, the Indy does not have a transmission flusher (BG, hotflusher.com) he said he flushes the cooler and transmission lines "manually". is that good enough? or is it better to go to the tranny shop that has a BG flusher?