How can I remove flaking (likely lead based) paint from very rough, exterior stucco?
What is mandatory for contractors is suggested for homeowners.  

Lead dust is what you want to avoid: 


Manual scraping is much better than power. 
Hand sanding is much better than power sanders
Wet wipe down is much better sweeping dry 
HEPA vacs are much safer than ordinary shop vacs


Common sense stuff: N95 (or better, EPA suggests N or P 100) dust masking, hand washing, clothing changing, sealing debris and plastic tarping in (appropriately tough, 3 mil ) plastic bags