OK, I left the missionary in Silverado for 4 turns and he failed. How long do you suggest he sit there? I see the benefit of having the OR bonus in Silverado, but trying to spread religion into a size 1 city that already has a religion is very difficult. Do we really want to risk wasting the 60 hammers we've invested in a missionary this early in the game? I'd rather use this missionary where he will have 100% chance of success.
The good part about the Missionary is that he isn't really tied to other parts of the PPP. So, we can change that one part of the PPP without affecting anything else in the PPP.
Our primary strategy calls for us leaving all new Cities religionless, in the hopes that Buddhism will spread there. Yes, the chance for each City individual is low, but if you add up a bunch of small chances together, you get several small chances.
So, I'm really hesitant to spread a Missionary manually to any City that does not have a religion in it, as doing so is against our primary strategy of trying to obtain Buddhism at any cost (to the point of settling really stupid Cities crammed in next to an AI that has Buddhism).
Or, spread Confucianism to Wheaties, since it will be able to benefit from the OR bonus very soon since it is growing and will soon be working the cows and possibly a mine giving it > 8 hammers (i.e. +2 hammer OR bonus). It doesn't have a religion either so success should be 100%, right?
Wheaties is in the same boat, at least until it gets a religion. If that religion is Confucianism, then we don't need to send a Missionary there. If that religion isn't Confucianism, we could seriously consider sending the Missionary there, as the City will be a bit bigger and is relatively close to the Confucian Holy City without being close to a different Holy City.
I do want to point out, though, that Silverado is the only City that can immediately benefit from the Organized Religion bonus.
Still, I would be willing to entertain the following idea:
Send the Missionary to Wheaties. Don't spread him. Let him sit there for turn after turn until a religion automatically spreads there.
If Confucianism spreads, send the Missionary to a different City that already has a religion in it. If a different religion spreads, then make sure that we've sat in the City for 5 turns without moving (6 turns counting the turn that you move into the City) before spreading the religion. Then we'll have been sitting there for a long time with the Missionary and will have maximized our chances of being able to successfully spread the religion.
The usefulness of sending the Missionary to the Great Person Farm is dubious
Now, I will point out that the Great Person Farm doesn't have much use for the Organized Religion bonus for quite some time. Presumably, we'll want to whip 2 Work Boats for the Fish before we complete the Granary. Initially, when we're working the Plains Cow, we may get a couple of bonus Hammers, but that'll at maximum only be for a couple of turns of growth, as we'll already almost be at Size 2 or will already be at Size 2, after which we'll whip a Work Boat and then grow using a Fish instead of the Plains Cow, so as to be able to whip quickly again. Only the second whipped Work Boat's overflow Hammers are Hammers that we might want the Organized Religion bonus for.
I still think we should spread Confucianism to the GP Farm right away. Play ahead fifteen more turns and you'll see that the GP Farm will be 1000% better since it will have access to the pigs and fish.
I'd much rather hire an Artist during 4 of the turns that we are Pasturing the Cow (it'll take approximately 7 turns to be Pastured by our Worker). In the grand scheme of things, the Great People Points generated by that Artist will have such a minimal impact on what type of Great Person we get for our 4th Great Person that I'm not worried at all about getting a Great Artist as a result.
Here's the related math:
3GPP * 100% * 4 turns = 6 * 4 = 24 GPP. GPP required for our 4th Great Person = 600. 24/600 = 4% chance of a Great Artist, 96% chance of a Great Scientist.