OK, I think I've got it now! Long story short, instead of resizing my pictures in Photoshop, then downloading them into Photobucket for labels (which I'm sure I could do in Photoshop if I had any clue how), I finally read through some of the help tips on Blogger. I noticed this feature a while ago but didn't pay it any attention, and now I see why it's there. Yeah, yeah, I know. Duh.
I paste the link to my Photobucket picture, hit the "Compose" tab in the top left while typing up the post, then click ON the picture. A handy little toolbar pops up.
Now all I have to do is select the right size, and in my case, X Large works perfectly. That's much easier for me than all the other rigamarole. See, now here's that picture of Tuesday!
She just walked in and meowed, so that's the Tuesday seal of approval.
I'm just happy that the answer was right in front of me, even though it took me a day to see it. Thanks, Blogger!