ya theres a guy who trades items for mini medals. There needs to be a guide for crafting items.
It's a pretty simple process, here's what I've learned from my own testing. The hotter the forge, the higher the range of damage you can do with a strike. When the temperature changes color, then the range values of your strike have reduced. This doesn't mean you always do less with subsequent hits, as there's overlap between the ranges for sure and it ends up relying pretty heavily on RNG.
Each bar of an item represents some amount of "health" with the green zone being a desired range of damage to do to that section, and perfection being a really tiny range within the green zone (on some things, perfection will be an exact number, and others it might be 2 or 3 numbers). There's some some algorithim that basically looks at "how far from perfection" you are in totality, meaning for all parts added together, and then assigns 0, +1, +2 and +3 outcomes to your result. I'm early on in the game, but I've found to get perfection on an object with 4 parts, I basically need 1 or 2 parts to be perfect (yellow) and then the other 2 or 3 parts to be very close. If you get all 4 parts close, or 1 perfect, 2 pretty close and 1 just close, maybe you'll get a +2, and if you just get 3 out of the 4 parts green (but the 4th part can't be egregiously off) then you'll get a +1. There's really a lot of RNG involved, as sometimes my first hit does 20 and sometimes it does 14. I just wouldn't sweat it too much, you'll always get the item if crafting from scratch, and perfectionist pearls make it pretty straight forward to get a +3 if you really want it.
With perfectionist pearls, the 0, +1, +2, +3 results are additive. So if you craft an item and get +1, then you rework it with pearls and that time you do well enough to have gotten a +2, it'll give you a +3 perfect item. Like I said, I'm still early on (Just left Hotto for the first time), and some of the items seem legitimately hard to get +3s on even 10% of the time, so save the pearls for when you find something that has a really good +3 boost. Several accessories are well worth considering, as well as the vest for success and what not.