McKay netted three times in 10 minutes after the break, with Nick Ross adding an eighth before Shinnie scored a ninth after his penalty had been saved.
Partick Thistle lost 2-1 in their friendly game away to Gateshead.
The home side went 2-0 up before the interval through goals by Rob Briggs and James Marwood.
John Baird pulled a goal back for the Glasgow side, who will be playing in Scottish football's top flight next season.
- Sports & Recreation
- Graeme Shinnie
- Ryan Christie