2: if it is, is there just a library I can use? 2a: if so, where is that library?
I Googled "attiny85 spi library" and got 35,800 hits, if that helps.
The big difference is that instead of SPDR you have USIDR. And you have to drive the clock yourself in software or externally. There's no automatic clock like there is on the 328P. And there's a different flag to check, but it works kind of the same. If you're doing what it looks like you're doing and sending out bytes as an SPI master, then the code in that thread should work just like what you've got there would on an arduino.If you want to run the ATtiny as an SPI slave, that shouldn't be too difficult to develop from there.
I had forgotten when I made the post above that I had written a small interface myself for the Attiny. All documented here:http://www.gammon.com.au/spiIn particular in this post: http://www.gammon.com.au/forum/?id=10892&reply=5#reply5