firstly--> yeah yeah for writing, it is so cool when they learn a new way to communicate.

my twin girls were busy writing up a storm when they were 4 and I approached both very differently when it came to spelling. One of mine is a rote learner with 100% accuracy--> so if she wrote "happee" and I never corrected it then it would be imbedded in her brain for ever that "happy" was spelt "happee" and it took more work and less enjoyment to correct it later than to just correct on the spot. The other twin was a girl who learns through praise praise praise and even a bit of praze (any spelling was encouraged). Both also needed an explanation, which is where I struggled a bit, they needed explicit "rules" to follow so that they would spell everything correctly first time every time. The best approach was simply to down tools for the week and do a crash course in spelling rules to avoid any frustration. They loath "exceptions to the rule" or mom/mum, color/colour type variations.

So a few tips:
*crash course in spelling rules
*lots of phonics games
*sight words just need to be rote learnt and I just found it best to have a chart of the 100 most tricky common english words and every time they were trying to write one of those they used the chart and knew not to use a phonetic approach (because it will never work)
*make sure it is well imbedded that many letter/s combinations make the same sound like g, j, dge or c, k, ck, or ee, ea, ie, ei, ey, y, etc etc and that failure to guess the correct one is more than likely to happen because the english language is crazy

I agree though, that the easiest way to address spelling is through reading--> they can spell years ahead of their peers now simply as they have read 100 times the volume.