In Javascript with steemjs (you can do it in the webconsole from https://steemwhales.com/post/ for example)

list = 'billykeed,tedcarr,meno,philfreetotravel,ninoleto,acromott,sunsurfsoul,jahissac,lovejoy,juanmiguelsalas,philfreetotravel,musiclover,jlsplatts,wearechange-co,ironshield,arthuradamson,sofietness,vannour,zkalemiss,mango369,dewallenband,trilumia,xtrodinarypilot,urukai,runamok,yann0975'.split(',')

for (numero=0; numero<list.length; numero++) {
  steem.broadcast.transfer('YOUR_POSTING_KEY', 'YOUR_USERNAME', list[numero], '0.001 SBD', 'Hi, here is your memo message', function(err, result) {
    console.log(err, result);
  });
}