Completely normal given the relatively large diameter nozzle (FN6?) and an 'orange peel' surface is fine, as long as you've not got too many large-ish lumps that might serve to distort the fabric once infused. If so, just smooth these down a bit with some coarse paper.
You might find that warming the gel coat a little prior to mixing-in the catalyst will leave a slightly smoother finish, but be mindful of the gel 'going off' quickly if the spraying takes more than 10 mins or so. The GC50 is quite thin already, so unless it's below 15 degrees C where you're working, it should still spray on okay
The cup gun is not such a precise instrument, but as long as you're spraying with a decent pressure it you should be able to get an even enough coating with a little practice.