I draw the whole thing, actually. I turn off the speechbubbles/text when I work on inking+colouring, so everything beneath the speechbubbles is still there, and drawn properly. I do this for Grassblades, but also for pretty much every other comic I draw as well.
Partly, this is due to my own need for neatness - and partly this is due to how I choose to promote the comic on other social media. I usually do it by cropping a panel out from the most recent page, and when I do that, I don't always want the speechbubbles in it. So I turn off those layers, and voilá - everything's there and properly drawn in!
Here's an example from my most recent chapter, first with text, then without:
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As you can see, though, I tend to compose my panels so that I'm aware of where the speechbubbles will fall. I want to be sure I'm not accidentally covering up something important.
