Knocking a lump off that chunk of rosin, pulverising it and dissolving it in just enough 95% alcohol (denatured ethanol or IPA) to get a liquid with the consistency of runny syrup, that can be applied to the work in a controlled fashion using a small brush bottle would be a good way to reduce rosin fume exposure, as sticking the soldering iron bit in the rosin to melt some for use causes excessive and unnecessary fuming.
Alternatively, just stick a flux pen on your next parts order. Any western brand of RMA flux from a reputable distributor will be fine, and will be less messy and more effectvie than making your own unactivated liquid rosin flux.