Not everyone is really confident about all aspects of the teaching of grammar so I would recommend getting a really simple book that explains it really clearly. I use Sue Palmer ‘The complete Skeleton book for grammar’, which I find is written in child-speak and therefore so use-able.
I also dip into idea books to help me think of short tasks for reinforcing skills or concepts. You can’t beat anything with Pie Corbett’s name attached and the Jumpstart series gives lots of activities that the children really enjoy whilst also teaching them the nitty gritty of writing. His poetry book is brilliant too and I use that for really reinforcing how language works and how it can be played with.