Is shoe polish a good or at least adequate solution for keeping a leather saddle in good condition? And/or better options?
I guess shoe polish (the creamy one, not fancier new ones with sylicone and lots of synthetic polymers) at least won't do any harm, but maybe there are better choices.
Manufacturers advise the use of specific products (Brooks Proofide, for example) both for treating the surface against wear and tear induced by friction and the elements, but also for treating the deep layers of the saddle thickness, improving its mechanical characteristics, specially when new and yet uncomfortable, but also after some use and possibly abuse (mainly due to weather).
Leather tanning actually takes the subcutanous connective layer of cattle skin, which is rich in collagen, and treats it so that it can last longer. As such (at least it seems so to me) they have a "natural" affinity for natural substances, specially the lipo-soluble molecules found, for example, in Proofide itself: tallow, beeswax, cod oil, etc.
I like to look at my Brooks as if it was a somewhat living friend: we have a friendship, I treat it nicely and it responds by treating me nice. Even caressing it and silently talking to it is fine (at least is makes ME feel fine).
So with the Proofide I like to think I am giving something it likes: those fatty, variated, long-chain, apolar, gracefully degrading organic molecules, and not the inorganic, synthetic, industrialized, unlively plastified synthetic products one might choose as an alternative.
(and by the way, the thinnest layer once in a while is more than enough: that tiny can of Proofide will last for many years!)
Shoe Polish is ok but it is going to smell and plus the seat will not soak it properly and leave traces on your pants.
I use a glove oil... You can find one in any sports shop ... just look for oil which is used to soften the Baseball gloves. I have used it on my Brooks leather saddle and have had no issues in last 2 years.
I wouldn't recommend shoe polish with any dye in it at all, because it's only going to get on your gear, and even "neutral" shoe polish is probably less likely to be formulated for a high friction application like a saddle as opposed to a shoe where waterproofing and "gloss" are the more likely goals.
I agree with the previous answer that a natural product is likely to have a better result than the synthetic ones, especially a combination of conditioning oil and wax, like the Proofide that Brooks recommends.
Do not use glove oil on a Brooks saddle. A saddle is a hammock in design, a glove is not, oil will break down the leather and make it eventually unable to handle the weight of a rider, and the leather will start to pull away from the rivets and you will have to adjust the tensioner a lot more frequently which will shorten the life of the saddle.
Brooks has been making their saddles for over 100 years, they know how best to treat their saddles. So follow only their care instructions and not some bicycle guru on the internet, or your local bike shop, or some friend, etc. Brooks even states in their warranty that the use of any other product other then Proofide on their saddle will void their warranty, end of story.