You only need to learn it once so learn it in Manual mode, it may seem daunting but once you have a few baseline settings you only need to actually adjust a couple of things per shot.
Oh and always have the lens square to the glass and touching (there is a plastic ring that stops glass to glass contact), the more you shoot at an angle the more distortion you get.
... and make sure your glass is clean inside and out, small smears create a light smear on pics.
Thanks Simon!