[Stylist] Spelling and Grammar Question

[Vejas Vasiliauskas]

Hi everyone, 
I was just asked by a friend to proofread a small piece they wrote and are hoping to submit to a magazine. They admitted that spelling and grammar are not their strong-point. 
I think it's admirable to recognize this, but I'm not really sure what the best approach would be from here. It needs a lot of work, and essentially needs to be re-written. I don't want to re-write it, as that would seem very patronizing. At the same time I feel that if I were to point out every single error, it could be too overwhelming. This is the second time I was given the article to look at: the first time I just mentioned that they needed to check spelling and grammar, but maybe I was being too vague because people aren't always sure what to do?
I'd really appreciate any thoughts. The message behind the article is great and I really feel that if it were phrased correctly, it would do very well. 
Thanks, 
Vejas