Its okay to mix products mate. Your missing out the polishing stage after the clay. If your polishing by hand you can't really use anything better than AG SRP, it contains fillers so will hide minor swirl marks and has some sealant to protect the paint.
I've only clayed my car once and its been over a year now and still looks good, although I do give the car a quick hand polish every 3-4 washes.
Zymol is good but expensive. Collinite is the best, 476 will do for your needs or you could use 915 but it has less protection and more shine.