Pick your developer. The best developer for PMMA is cold IPA+water (3:1), which we keep in a dedicated tank in the YINQE lab. If someone tells you to use MIBK-IPA mixtures instead, they are very much out of date. IPA-water is better in every way: higher resolution, less residue, less swelling, higher aspect ratio, lower toxicity, and lower cost.
ZEP can be developed in a wide assortment of chemicals, depending on your needs. There is a tradeoff between sensitivity (speed) and resolution. If you need to expose large features quickly, then you can use hexyl acetate as the developer. But most people use cold xylene to develop ZEP, since they need the best resolution.
When developing HSQ, there is a tradeoff between resolution and stress. That’s right: strong developers are used for the highest resolution, and these developers require very high electron doses. High doses shrink the resist more than low doses, leading to more stress in the resist film. Depending on the pattern, HSQ might peel off, crack, or “unzip” due to stress. That’s why people will use patterns of dots and short lines to show the highest resolution. For more practical applications we use a weaker developer. Around here we usually develop HSQ in MF312 (which is 0.54N TMAH) for 4 minutes.