It is hard on any piston-and-cylinder engine to put liquid solvent into the cylinder - whether it is petrol or some other solvent is not all that important, what matters is whether oil is soluble in it. That is why I tend to recommend priming engines through the carburetor air intake rather than through the sparkplug hole: you can hope the solvent will be in vapour form by the time it enters the cylinder. Some of the solvents mentioned are even less suitable than the others; in particular the solvent sometimes used in flyspray and some other pressure packs is kerosene, not petrol, and this is not a good fuel. If the engine starts at all on kero it will probably detonate. Things like hairspray have lacquer in them and you do not want this inside any part of your engine.
Most pressure packs - degreaser is an exception - usually emit the solvent in atomised form, so it is likely to vaporise on its way through the throttle, intake manifold, and port. I think you can still buy spray cans of ether for starting engines, but it is relatively expensive and in my experience only marginally effective.
In a technical sense, squirting hydrocarbon vapour into your engine is less harmful than using a primer bulb (which squirts liquid petrol into it). That is one of the reasons I was much happier with Briggs' old chokes than I am with their new primer bulbs. The main point though is that if there is nothing wrong with the engine you should not need to do anything other than follow the manufacturer's starting instructions. If it won't start reliably by doing that, fix it. Yes, keeping a can of ether near a fire pump or emergency chainsaw is an exception: if you end up completely ruining the engine starting it that way, that is a trivial matter so long as it did the job once, when you needed it.
