I'm on MDI and only use insulin for meals because my fasting BG is pretty good, so far, and my endocrinologist doesn't think I need a basal insulin yet.
I divide meal boluses all the time, especially in the morning when I eat mostly protein and almost no carbohydrate for breakfast. I find I have to cover for protein and fat, so I calculate the insulin based on 58% of the protein and 10% of the fat, then take about 2/3 of the bolus when I finish the meal and the remaining 1/3 about 90 minutes later. This keeps my PP BG from spiking and also helps with the slower digestion of protein. When I have carbohydrates in my meal--usually for dinner--I calculate the insulin needed for the carbs as well as for the protein and fat. I take 2/3 of the bolus just before the meal, and the remainder about an hour later. If it happens that I don't eat everything I expected to eat, or decide to eat more than I'd originally planned, I can make adjustments, reducing or increasing the top-up bolus. This has worked very well for me so far.