My vocabulay book exercise says it's wrong to use a bit and a little with adjectives before a noun. For example, It's incorrect to say
It was a bit small flat. (flat as a noun like an apartment).
The book suggests the reader to use slightly instead. Now I'm wondering whether it's correct to use other adverbs such as: fairly, extremely, incredibly, pretty, rather, quite, etc.
Does the exception only hold for those two I've mentioned in the title and always work with others?