Adding some more fruit during primary fermentation

[Rhetoric]

My first time making wine. I have a small garden in my downtown city house in Hiroshima, and I've had grape vines growing for many years. This year I had a bumper crop of purple and white seeded grapes so, without washing them, I mashed them in a 5 Liter bottle with a big mouth and added some water, brown sugar and a little honey. Now it's two days later and the natural fermentation seems to be going well; its bubbly, smells yeasty, and I swish it around a few times a day so the pulp, which is rising to the top, settles back down briefly (and bubbles alot). Aside from any random observations, which are welcome, a few specific questions:

When I was harvesting the grapes, I missed a few bunches, and thought, why not add them in now? Is that a good idea?

I scored some blueberries from Costco. That would make for a nice addition to the flavour, could I add them in now during primary? I was thinking to blanch them with boiling water (to kill bacteria) and throw in a packet of Pasteur Red Yeast while I was at it, to make sure the natural yeast is helped by the targeted one.

My limitations should be noted. In Japan, it's technically illegal to brew anything above a 1% alcohol content, though this is practically unenforceable. However, there are no winecraft stores. Stuff is available online only, for prices that vary from three to ten times more expensive than the U.S. I got a secondary fermentation kit, and some yeast. I'm still awaiting the hydrometer and the campden tablets, which were a bit more difficult to get, which is why I started with the natural yeast only.

Additional question: I haven't yet ordered the hydrometer, there's only a few types available for purchase from Amazon Japan, and I'm thinking of going with the Abe Advanced Optics Refractometer in deference to the standard triple scale Brew Bros. hydrometer. Since I only have a small batch, it looks like you have to waste a 100 ml or so of the primary fermentation batch, the must, just to measure it (in addition to dropping the temp. to 20 C.) Alcohol content/specific gravity appears to be measurable with a few drops from a pipet instantaneously with the Refractometer. Any thoughts?
https://www.amazon.co.jp/s/ref=nb_sb_noss?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&url=search-alias%3Daps&field-keywords=hydrometer+wine
(This page shows the types of hydrometers available in Japan.)

 

[mennyg19]

Adding more fruit shouldn't be a problem at all, just be careful, as the new sugar from your new fruit will raise your SG. Heck, there are people on here that add fruit after their wine is finished entirely in order to get a better color.
You don't have to waste 100ml of must to measure. You can drop your hydrometer right into ur primary in order to measure it. As long as you sterilize the hydrometer first it wont be a problem.
Dropping the temp is recommended anyway for a better, safer and smoother ferment. If thats not possible, you can use the hydrometer with the temp higher, but you will have to convert the reading afterwards. The hydrometer usually comes with a guide on how to convert. You can also check online. The higher the temp, the higher SG reading will be from what you see.