I found if you want to bait them then try this: a pound of hazel nuts from your local supermarket, put in food mixer processor type thing and grind them up coarse( large bits are best), put this into a plastic container the type you can seal, as the nut oil is what attracts old Mr Tree rat and you dont want to loose any of this.
Once on your shoot empty the bashed up hazel nuts into a pile close enough to your hide to get a clear shot, sit back and wait for squirrel to arrive and kill him,

simple.
Ive tried this out in one of my shoots where there are lots of natural food stuff and it worked fot me. The time is fast approaching for them to hoard food and the squirrels will active in making sure they have enough for winter, prime time for squirrel bashin.....................
I have a squirrel call it just attracts magpies

He He
Good luck and keep us posted.
Les