Would mixing quick setting & regular be a bad thing or would it be fine.

I don't see why it wouldn't work but just wanna make sure. I just don't think I'll have enough of one.

Who knows
Grow a pair and just do it. Worst case senairo it doesnt work and you gotta resand it and buy a tube

I think if you mixed them separately, and then mix them together to make the application to where ever that is your best bet. That's my opinion, I have never tried this at home.

it would be fine.