this two lenses are not best for macro but you can try to use reverse ring on 18-55 lens or buy macro lens but revers rings are much much more cheaper and i think its a best way to start with macro photography if you find yourslef in this type of photogprahy then you can invest in proper macro lens and lights.
I’d just get a diopter to screw into your lens. The 70-300 is a better candidate if you want to control your light and maintain distance to your subject. A diopter also maintains all lens functions. A reversing ring doesn’t and your focus distance is fixed also. Reversing rings are only nice for e.g. a 50mm prime. Extension tubes or macro bellows are other alternatives, and having a true macro lens is of course wonderful.