"Some with swivels...some without":---I personally like them with swivels on the back end.....other people do not. A swivel up front and a "hangback" hook with a swivel can change the action of the lure. Because the spoon has more hardware hanging off the back end, it tends to stop the spoon from flailing wildly as much when fished faster.
And the heavier hook you go the more this is true. Swivel upfront:- many regard this as blasphemy.....I like it myslef...and many factory spoons come like this.....but others avoid the swivel up front like the plague. When spoons like this are fished at normal speeds...they work no problem at all.
Pros and cons abound.......but at the end of the day ,do they work rigged like this and get fish in the boat?.......yep.
Leader length.......it can have an effect on the spoon behind a flasher......some people I know fish small spoons right down at 38" or less. Myself I like them about 56 to 58"...but there are days when I just go "normal" at about 5 or 6 ft.
I like to know what's what so I always mark the leader length on both spoons and hoochies.
Paint:- I get the enamel model paint that comes in little tiny bottles, nothing special, at hobby stores.....but if you just want to try one temporarily.....you could use colored nail polish.
The molded eyes are available from different places at times......I use clear marine epoxy and glue them in place because if you just stick them on they don't stay on very long.
Be aware that such things as molded eyes, hangback hooks, and swivels at both ends can all have an effect on the lure action. I sometimes will put extra or less bend in the body of the lure as I see fit.
One can theorize all day on the pros and cons of spoon construction/design.....but what really counts is if they work for you......
I find that a spoon with an eye on it ( I usually use the "glow" eye) works better than a spoon without one......but that's just personal choice.
I have mixed feelings about running a spoon on a short leader behind a flasher.
A flasher rotates in a certain direction...
The flasher on a short leader will tend to want to encourage rotation on the spoon because the leader is always rotating.
And the flasher actually makes the spoon go faster through the water because of the amount of water covered in revolutions.
If the spoon is way back....5 or 6 or 7ft...this effect would be less.
If no flasher at all the spoon will track correctly through the water and tend to work as designed. But it will be in a wobbling straight line as compared to the wild action of a flasher.
So larger mature "returners" might like a lazier straight-track spoon than a psycho piece of metal behind a flailing flasher......
But you never know.......strange things happen when fishing.....