Yes, you can. 'Quite a lot of' can be used for both countable and uncountable nouns. The meaning isn't always exactly the same, however. Depending on the context, and other factors such as tone of voice, 'quite a lot of people' might suggest a greater number than 'quite a few people'. But in general - and if it makes life easier for you! - you can usually replace both 'quite a few' and 'quite a bit' with 'quite a lot'.

Well, grammatically it's true in both types of nouns (uncountable and countable), but in terms of senses they make it can be interchanged with none of them. "A lot" implies a high amount of stuff while "a few" and "a bit" denote a low amount.