I was a silent hill nurse last year and again this year (we've upgraded with costume contacts and better weapons! woo!)
anyway, to stain our dresses, we used a mister (erm, that looks weird... a spray bottle set to fine mist) and then over the course of a week layered on different mixtures of coffee, tea, diluted green/brown food colouring (to look like mold), etc. - anything we could think of really. for the mold colours in particular, we used a less fine mist so there were visible spots. its best to let dry between the mistings because everything would kind of mix together if it all got too wet. and, btw, no smells. then for the blood, we had some store bought blood gel that we used to make hand prints, streaks and splatters on the dress. i found it looked too fake, so we then made our own blood with this recipe:
Dilute K-Y Lubricant with water until you get a syrupy consistency, add some flour or white frosting mix to make the mixture opaque, then add red and yellow to get a good blood color. add a bit of green food coloring to get reddish brown. Real dried blood is quite brown, but it'll look better if its still a bit red. apply and let it dry. This mixture has a great looks when it is dry.
this recipe was amazing, made great dark crusty blood. we used the mixture to layer over the other fake blood and, together, the two give a new and old blood effect. we also went outside in the full costumes and had someone whip gobs of the blood at us to get realistic spatter patterns. i think that is all we did to the dresses, hope its helpful. oh, we also used iron on transfers to put the red cross and Brookhaven Hospital logo. these are like, seriously, the funnest costumes ever to wear. we SCARED people ^_^
here is a shot of the dress... i'm not wearing the mask in this. i suggest making a removable mask and then doing makeup underneath, it gets hot wearing the masks for too long in a club.
btw, this is from last year - i will post the updated costume when its all done.