So, when I did my original research into how I was going to grow, I had a plan. Solo cups till I see a 3-fingered leaf. 2 gallon buckets for vegetative phase. 5 gallon buckets for flowering phase. Now that I've an autoflower starting to flower and two other plants in mid-veg, this is beginning to seem like it will wind up being a hassle. Should I go strait from solo to 5 gallon, or am I doing it right?
Yeh, I would go for 5 gallon. Repotting can be a big PITA, and I really do think your original plan is the best. But if that's not practical, I would go straight to 5 gallon. Oh, if at all possible, try to use the same kind of soil every time your repot. When I repot I always make sure I have plenty of drainage, and I always water really heavy starting out. New soil sucks up a ton of water.
I can keep swapping them like that, if it won't over-shock the plant. I think the original thought was that going strait to the 5 gallons would screw over the plant because all the nutes and water would be too deep in the pot. Generally, when I repot, I take the 5-gallon, fill it with soil with an empty 2-gallon buried in it at the surface, and just completely soak the soil a few times. Then I remove the empty 2-gallon, and replace that space with the plant. That way, the NEW soil gets a ton of water without drowning the old soil. Does that make sense?
Go straight to your final pot. You can check the auto grow in my sig. I planted into 5g nursery pots and the plants are far from stunted. Just be careful not to over water, specially the first week or two. Repotting is realy not needed to form a good root structure. Your repotting method is exactly how I do it as well, it works great.
Here's how I repot. I make sure I'm using the same soil. This limits transplant shock. I take my new pot, and make sure it has good drainage, and then I fill it up with new dirt. Pack it down a little and dig a little hole in the center. With the old soil, it's a good idea to try to not disturb the old soil and the roots. I let the soil dry out after the last watering until it's just a little bit moist. I squeeze the pot so the soil sticks together, and just put everything in the new pot. Then I back-fill with new dirt. Pack everything down a bit and water it heavy. After that I don't water them too heavy for a while. It takes a while for the roots to make use of the rest of the pot.