How much can I concentrate/reduce GD for solvent transfer?

Since you used 192 proof alcohol you can reduce your tincture as much as you want, even less than a few ounces. You may not want to go all the way to RSO, but you could. You should end up with your same 10 ounces of oil once the alcohol is evaporated off. Good luck with it!

 

I make a lot of tincture, then remove the alcohol with some distillation devices, and replace some of it with oil.
The way I handle mine after distilling off most of the alcohol is to heat it up on a covered stove burner with the oven's exhaust fan on, and an overhead fan on.
Then I heat it quickly to about 225 F, while stirring with a candy thermometer, so that all the water will boil off.
Whatever volume is left will add to the volume of what you add it to, meaning that if you end up with 10 mL FECO mixture, and add it to 90 mL of something else, the total final volume will by 100 mL.

 

It's really up to you as to how you get it done. My very first GD was used as a solvent transfer for the first honey I made. Once I discovered what I had done I started thinking about doing it for other mediums like oil, butter, agave and anything else, if possible.

You can reduce your GD as far as you want. The more you reduce the less heat you will need during your transfer. Let's say you have 10oz of GD and want to infuse that into your MCT, 10oz. You can add them together at that ratio but it's going to take a looooong time to finish evaporating, a few hours maybe. Maybe enough to start degrading it depending on your heat. It's not going to be much and would depend on the total volume but it's best to avoid that if possible.

So, my suggestion is to reduce your GD by half or more to concentrate it more so that you're using less heat. It's pretty much the same with smaller as well as large projects except that the larger the project the more heat you have to use to make the transfer. If you reduce the 10oz of GD to 2oz it will still have the same total cannabinoids as the 10oz but you only use 20% of the heat (and time).

Definitely take it to 2oz for the transfer. It will be fine. Keep in mind that your total potency is in that 2oz of GD but your dosing will be with that 10oz of MCT. Let's run an example:
If your flower is 15% THC, 150mg/g, and you're using 28g then you have 4200mg total availability. We extract about 75% which leaves us with ~3150mg in your concentrated 2oz of GD. That's how much you have and that will be transferred to the 10oz of MCT oil.

So your 10oz of infused MCT oil will contain that same 3150mg except that now it's distributed over 10oz instead of two. Each oz of MCT has 315mg/oz or 10.5mg/ml. And if you wanted to double that you would transfer those 2oz into just 5oz of oil. The ratios are easy to compute.