Thinners and reducers are 2 differnet things.
Thinners are very harsh and is used only in Lacquers and cleanup, Reducers ( and each product requires its own) are for the alyklid, acrylic, and Urethane base products, and not as harsh.
Using thinner in you synthetic primer will only make it dry faster , but will reduce its quality of the product. Does it require a hardner(catylist)
Why dont you throw that stuff away and go to your local Automotive Paint Jobber and get the correct stuff you need. I am not into using off brands, this way you can get everything you need thats compatiable .
Have you emailed that company you bought the primer from to see what reducer it takes ?
PPG, Dupont, Sikkins, all make quality primers that are tintable,.............. expensive? yes but way better products!!!!!!!!
SprayTech