Have they changed the formula ? I used this stuff a long time ago when I was a dispatch rider and my bike used to eat chains. Found it to be no better than spray lube plus all the hassle of taking the chain off- thank heavens for O ring chains, I got nearly 25000 miles out of the last chain on my Kawasaki ZZR 1100. I would fit one to the BSA but the clearance is tight with the chain guard.
ZZR 1100 for dispatch riding.
You obviously like doing things the hard way.
I did the same job in the Sydney CBD on a SR500 with the A65L as back up .
Both bikes had a 200 litre combined pannier top box fitted into which I could jamb 300kg of airfreight satchels.
As for fitting the chains, that is why you use multiple chains.
Just link them together and pull the new one in with the old one.
I used to buy my chains by the roll .
Once a chain has reached the end of the adjustment on your rear wheel the sprockets have significant wear.
The trick is to run several chains so all of them wear with the sprockets.
Putting anew chain on a set of worn sprockets will kill the chain in no time flat.
When we were in the mountains I was knocking up a touch over 150,000km / year and was doing a roll of Hitachi industrial high speed chain ( 100 ft ) about every year.
The M20 has not gone through it's 5 chains that I bought back in 1994 and that is well over 500,000 miles ago .
It has gone through more pistons & clutches than chains