i plan on making SENTINEL costume from marvel vs capcom 3.
take my noobie quesiotns and ill give you a sentinel costume!
I don't even know what a Sentinel is, so I'll just answer you for free if you don't mind.
1.) inhaling resin is bad. but when its dry, its fine to breathe in your helmet?/ smell no longer there? how is drying resin safe to breathe in helmet? anyone know the physiology behind it?
First of all, you don't inhale the resin. Doing
that would kill you really fast and really permanent... would be like drowning, only water is a lot thinner than resin.
What you are talking about are just the fumes emitted by the resin. The smell, so to speak, assuming the fumes have one. There are different kinds of resin, and they all work differently, smell differently and have different effects on your body.
I'll just assume you're talking about polyester resin (aka "fibreglass resin"), that's the one with the strongest smell. What you mainly smell there is styrene, which is a solvent. Other than in most paints, however, it doesn't just evaporate and leave some solid stuff behind, but it actually takes part in the reaction that takes place when the resin cures (side note: resin does not just "dry", it really does react, i.e. change chemically) and becomes part of the finished material. The stupid thing is: When something reacts, there are usually some stray atoms/molecules that don't take part or don't do so right away. Any such styrene molecules can still evaporate, even when it seems like the reaction is over. Adding more hardener (which, in the case of polyester resin, is a catalyst, i.e. stuff that makes the reaction happen, imagine it like a kick in the rear for the chemicals) speeds up the reaction and can reduce the time during which the cured resin still smells, but it will smell for a while, a few weeks at least. The smell will go away eventually though and it is safe to breathe while wearing a finished helmet.
The physiology behind it... 3M has a pretty nice MSDS for their fibreglass resin, you can find it with Google. All the health effects are neatly listed in there, most are caused by the styrene.
When using polyester resin, wear a respirator with vapour filters. If it's white and soft, it's the wrong one. You'll also need gloves (heavy chemical ones if you plan on working the resin with your hands) and safety glasses. Keep in mind that other resins may require different safety measures. Epoxy, for example, fives off far less dangerous fumes, but is far more dangerous when you touch it.
2.)inhaling fiber glass is bad. when putting coat of resin over it. theres no way to inhale it in your helmet? or can you?
If you do it right, the resin will completely envelop the fibreglass, so there's no way for it to get out unless you break your model. I've also read contradicting advice regarding the inhalation of fibreglass particles. Some sources actually say something about it being natural and degrading in your lungs over time... I don't believe that though. I think what they mean to say is: It's better to breathe in fibreglass particles than asbestos particles.
You already bought a great respirator with perfect fit after question 1.), so just get particle filters for that. If you can, get some that you can put on top of the vapour filters, because you'll need both filters at the same time, e.g. when spray painting.
3.) best way to get rid of paint smell ? or why use spray cans vs acrylick, which has no smell?
Just give it some time.