As for tools and such, it all gets down to what you have and what you are good at doing.
I've known folks who could paint intricate detailed figurines, but mashed up their finger opening a jar of jelly.
Likewise ones who could do micro soldering, but could not draw a straight line.
If you combine tools you already have with skills you already possess, then your chance of a good repair goes up.
Otherwise you need to practice so your hands and tools do what your mind wants.
A soldering iron with the right tip and temperature can CLOSE and seal the wound.
But it also runs the risk of melting and deforming nearby TPE.
Thus you can quickly make things worse if you are not practiced and skilled.
A soldering iron can be used to smooth. But you need to use the side of the barrel or a spade tip.
Using that you run the risk of digging in and causing divots which then need to be smoothed.
So unless you have a really fine touch or done stuff like that before, probably best to avoid an iron.
A temperature controlled heat gun used for electronics work really works well for smoothing.
Not a hairdryer or heat gun used to strip paint or shrink film. Please don't use those.
An electronics type heat gun allows you to set a specific temperature and airflow, the others do not.
Another way to smooth is the HOT SPOON method.
For that you heat a spoon or other tool and use it to knock down the pre oiled TPE to smooth it.
You don't need to use an actual spoon. I've used metal sculpting tools and even small metal shovel items depending on the application.
Whatever tool you use, make sure the tool can handle 150-175C temps and you wrap the handle to avoid burns.
If this were my doll knee, I would smooth using a combined approach.
First apply oil to the target area and pre heat with a temperate controlled hot air gun.
Heat the TPE until it is pliable, but not flowing. The TPE will retain the heat for awhile and help in the next step.
Next I would use some preheated tools to do the actual surface smoothing.
For that I have a small solder pot that is filled with oil and kept at about 160C.
I then take a pre oiled and preheated tool and use that to smooth the TPE.
After a few passes the tool cools and goes back into the bath to heat and I use another one.
If you don't have a hot oil bath for your tools, you can heat them with your hot air gun.
Surface texturing is just to remove any surface glean by giving the TPE a semi random stipple, similar to human flesh.
All you need is the TPE hot enough to be pliable and accept an impression and a material to make the impression - WITHOUT CONTAMINATING THE TPE.
The last is key, since any dirt or grit on the impression material will bind into the TPE and make a bit of a mess.
Personably I use 3M Wet or Dry Automotive Refinishing Sandpaper in really fine grit, other similar sandpaper would probably work fine.
Avoid dry only stuff, coarse grit ones, those for woodworking and really cheap stuff. The grit tends to come off and embed in the doll.
Before use wash with hot water and soap several times to remove any excess grit and make it a bit more pliable.
I make sure never to use it to actually sand stuff. This prevents contamination and keeps the grit sharp for texturing.
Use is pretty straightforward. Heat the pre oiled TPE with hot air, gently press in to apply texture and repeat if needed.
I usually mist some iso alcohol over the area once done to flash set the warm TPE surface and get an idea of how it turned out.
When all done let it cool for awhile to make sure the TPE is fully set and your flesh impression stays intact.
It is pretty simple to do and hard to screw up, but if you have never done it before then practice first on a hidden area.
Hope it helps.
Cheers!
... W ...
