I researched flying into Glasgow some time ago. Handling is mandatory and the total cost is expensive even if you visit the flying club there.
As GTE suggests, I fly in to Prestwick a couple of times a month. I rent a car from Avis which is delivered to and collected from the Prestwick flight centre. The drive to Glasgow city centre is about 45 minutes.
The process of getting into and out of the airport is very easy and the total cost including the car is about a quarter of what I recall the cost of landing at Glasgow would have been when I researched it.