With a CYA level of 270, you'll be adding it 1 - 2x per week.

Add 5 gallons; wait 4 hours and then test. If it's really 10% bleach (and if your gallons figure is accurate), you should see a chlorine level > 20 ppm.

Assuming all goes well, add 5 more gallons the following day, to get yourself closer to the 'can kill algae w/ 270 ppm CYA' level.

Using the HEDP is fine . . . but keep in mind that it's effect is temporary. To REMOVE the copper, you may need a CuLator unit, OR to do some shocking with calcium hypochlorite shock. (BUT, get specific direction that DIFFER from label directions BEFORE doing this.)