if its just for the boot floor just use the respray kit , will probably the cheapest option and as for shine you could paint the full car with it no problem as its good stuff .

but for resprays a always use base and clear but again just matter of opinion as is a dearer method but means you cover your back if any shit lands on the job or that , u can just give it a scuff and recoat it so its all perfect for clearcoat .