A great tool for scheduling meetings via LinkedIn is (https://linkedhelper.com/). It automatically sends invitations with messages attached.
Over a 14 day trial it sent out 840 invitations with this message (Hi (name), I would like to connect because I am interested in your feedback. I recently left my job to launch Scribbl.co)
Co-founder @ Scribbl.co
Linkedin is cracking down on such automated tools. I got a warning from them saying don't do it again or we will suspend your account. I was using another tool though.
By the way, Scrbl looks very interesting. Good luck
Aji