Check the seat post with a micrometer. There is tremendous variation brand to brand and model to model between seat post sizes (diameter). Use one that is too large, and you will probably end up with a stuck post. Use one too small and you can damage the seat post clamp (the bike frame). Doubtful it will be the right size.

Personally, I avoid frames that need paint. I use those bikes as donors, unless they are some unique high end model (which does not appear to be the case in your example).

Financially, I would sell the Fuji hybrid, and use that money to buy a good 1980s bike with standard bike sizing. There are a lot of great bikes from that era that you could buy for what that Fuji brings. Heck, if you do the thrift store/garage sale circuit, you can probably find something pretty decent for around $20 to $30. I find that I can rehab such a bike (new cables, tires, tubes, bearings and grease) for less than $30. At that point, you have a winner!