Lochwinnoch to Port Glasgow on old railway lines
Glasgow to Loch Lomond (Balloch)
Balloch to Tarbet along the west side of Loch Lomond - mainly cycle path
Glasgow to Uddingston NCN 75/Clyde Walkway - mostly cyclepath but some on road. There are a few gates just after Glasgow Green but they have been open when I have cycled this route. Unfortunately there is a barrier just as you get into Uddingston which is always closed. NCN75 continues on to Edinburgh but I have never been able to find the direction signs once I got into Uddingston. The Clyde Walkway goes as far as Strathclyde Park, but again I have not found signs - this would be a nice ride to the park and back to Glasgow Green which I will research further.
Glasgow to the Falkirk Wheel along the tow path of the Forth and Clyde Canal (path continues to Grangemouth Marina). There are too many gates and barriers on this route for me to recommend it for handcycling - although it is possible with some help.
SUSTRANS Access for Disabled People in Scotland - Access audits on several traffic free routes across Scotland