I have been working with an 8 year old pupil on the spelling ‘ck’. We also need to revisit ‘sh, ch and th’ which she tends to forget and confuse. Every week we do a bit of dictation including the graphemes we need to revise. This dictation is based on a Dandelion Launcher book ‘Which Shall I Pick?’ in Unit 14. (It makes more sense to use a decodable text as a context for dictation as it is linked to what we have been reading).
What is so great about dictation is that my pupil can succeed in spelling words in this controlled dictation which is aimed at her level, while revising the graphemes already covered. This activity requires her to recall and form the corresponding graphemes to the sounds in the words she hears. As she has learned all the graphemes she can succeed. She was very proud of her achievement today. At the end she reread her work which entailed practising reading. 
A truly multi-sensory exercise! That’s what so great about dictation!
And I just thought about another thing: It is a really good opportunity to model punctuation as so many children seem to have such difficulty with this.