I've collaborate now with everyone (except for COTU world) who I looked at in the beginning and wanted to have a go at resin production myself. I'll update with details when I have them.
This isn't going to be a guide on how to cast for complete beginners, more a few things I've come up with along the way to help me with troublesome molds, and to save materials.
SILICONE STICKS TO SILICONE. MAKE THE MOST OF IT!
You probably know what a waste mold is - it's where you make a mold using waste silicone. Any silicone that isn't covered in mold release will bond with whatever curing silicone is next to it. Think of it like hardcore and concrete. Hardcore is cut up pieces of old mold, concrete is the new stuff which bonds it all together. You will need a pressure pot for this to work though.
All of my large molds are made with a lot of waste silicone.
I did a quick vid on instagram how to replace part of a mold that is mostly fine: https://www.instagram.com/p/BKbE1pagMXK/?taken-by=bigmantoys
As long as the original model is strapped in tight, the mold should be perfect. The rest of the mold will still give way eventually but these weak spots can be fixed several times. Here are the results of the above video, you can see the shapes that will make the negative shoulder articulation- ive already had perfect pulls from it:
RESIN - IT'S BETTER TO WASTE A LITTLE THAN WASTE THE LOT.
By that I mean, "topping up" molds where you haven't poured enough, or having bubbles because you didn't cut fat enough ducts make the sacrifice of a bit too much resin worth it.
With really bad undercuts, like the back of Blade's hat, I use a method of letting it leak. You can see that I've sculpted him so everything except the hook (which can be vented easily as it's near the feet) is facing upwards, meaning I could in theory have just one vent from the hook to the leg, and one from the feet to the bottom and I'd be fine.
Pull out the stick - it creates a vacuum, rushing material to the hole on the side.
OTHER GUERILLA METHODS
I learned with plaster before I used resin or silicone, and then i tried casting without a pressure pot or vacuum. I learned some stuff that still comes in handy.
1: Air can't go where something solid is.
I sculpted this giraffe head (Im putting this custom in store BTW) with horns at the top, they are narrow with bulbous tips, meaning theres an area that needs resin with a small amount of space for the resin to get though. Also, down at the bottom of the mold, air will get trapped there first.
2: Poke, bang, and rock.
If you're casting something really thick, or are casting without a pressure pot, you can minimse bubbles in a few ways. You can poke the areas where bubbles happen before the resin cures, with a stick, you can bang the mold from several angles to try and smack out the bubbles, and you can pour a little resin in, and rock the mold. With only a little resin, rocking should make a shell inside the mold wihtout enough liquid to trap air (bubbles). Once that's at least half-cured, you can pour in the rest. Any bubbles will be internal, where you can't see em!
WHATS LEFT IN THE CUP
I try to always have a mold at hand with a wide opening that I can pour into quickly. All my leftover resin after a pour goes in these, and after a few pours, I end up with some bonus casts.
Also, I've recently expanded my Bigcartel store (upgraded account) and am putting in EVERYTHING I have in the studio. I'm really low on space so it's all priced to fly. http://bigmantoys.bigcartel.com/