It is a good idea to have an MSDS sheet handy, your seller should provide one. In reality, MSDS sheets are always worst case condition. If you read a number of them you will see that they are almost all the same and are based on a formula. For instance it lessens any liability and most say that for any skin contact you should seek medical aid immediately after flushing with water. With gum printing we are not going to dealing in these extremes.
Hexavalent chromium can however be dangerous, no doubt about it, but it can be dealt with safely.
First off let's deal with our personal safety. Gloves are essential. Of course follow common sense rules. A paper face mask is needed for weighing and mixing the dry crystals. If drying the coated paper with a hair drier or fan a face mask would be a good idea.