Well not easy you do have to stay on top of your game and not let focus stay full too long. It's 4 days worth of playing (6x4x24x4=2304 shards[6 wins per hour x 4 shards x24 hours in a day x 4 days]) to get the cards with extras. But sleep will rob you a few of those. That's with only 6 hours of sleep a day (24 hours) of missed opportunities for me. 6x4x24=576 missed shards. (1728 total without pause for anything other then sleep)
if you only have the N-slayer it's harder (6x2x24x4= 1152 shards). You will get at least 2 shots at the other slayers because you get an E-gatcha for logging in, and one from consecutive wins. you do get a few for streak/daily wins but not enough to make a huge difference.
I will get a third shot because my monthly E=gatcha will arrive before the end of the event. Of the 51 cards in the e-gatcha box I am missing 16 (that's 31%) so I have a good chance of getting at least some missing ladies.
Happy hunting.
P.S. Yes, I do agree it's a poorly thought out event.