Hello Centaurus.
Don't know if it is any help, but here goes.
About 100 years ago when I got into this game (well, it seems that long some times), I was told/taught a thousand things, most not written down.
One of those things regarded radials. Being as radials have some cylinders that are discriminated against by gravity, it is of the utmost importance to ensure that you turn through a number of blades. On those installations that can't be reached due to elevation, then you must turn through on the starter.
I have seen the RNHF remove the lower plugs before putting the Swordfish to bed. I have turned nine blades on the starter on a DC6 before priming and ignition. I have walked through 9 blades on DC3's. So far, I haven't played with single row P&W's, and therefore can not advise specifically.
Perhaps an e-mail to some of the floatplane operators in the USA or Canada might solicit a benificial response.
camlobe