I wouldn't use spray stuff while on the bike and able to get onto other surfaces like braking surfaces unless I was able to clean them with isopropyl alcohol. You never want to spray anything on braking surfaces and want to avoid getting things on paint if they cannot handle paint well (check with manufacturer). You can certainly use some plastic bag or even a piece of cardboard to help prevent overspray but I would rather just get the cassette and chain off and spray those in a bucket or bin or something away from the bike.

Don't contaminate your disc brakes. Spraying random liquid from a can or whatever that isn't alcohol or a formula specifically designed to clean bicycle disc rotors and pads is going to contaminate your rotor and pads. You will need to clean with alcohol and potentially burn it off especially if it contains oil. You will want to do a controlled burn in a fire safe area and have some water or a fireproof cover ready to contain if it gets out of hand but it shouldn't if you are careful. Alcohol shouldn't cause any permanent swelling it will evaporate or if you burn it, it will burn off you might have things backwards if you think 70-90% isopropyl alcohol is causing swelling.

Also make sure if you aren't burning or are wiping something to use a clean towel (paper works great) that hasn't been cleaned in oil (some shop rags are cleaned in oil). And don't touch your braking surfaces as the oils from your hands can contaminate things.