Pre-emergent weed control...HELP!?!

Ok I have a question. I am starting to do pre-emergent applications this year. But, most of the yards are established lawns with weeds already in them. Should I mix pre-emergent and post-emergent granulated weed control and spread it at the same time? I figure that way I could kill out the existing weeds and also prevent other weeds from growing. Or should I just do one or the other? If so which one? Also, I was planning on aerating before I apply the pre/post emergent. Should I mow, aerate and then do the application or can I just aerate and apply? The reason I am asking this is because it really isn't time to mow yet but I would like to get all this stuff out of the way now if I can. If anybody has an answer or can explain the best way to go about this it would be greatly appreciated!!! Thanks guys.

[Steve]

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Does anyone have any advice on this?

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well i already did one yard...hopefully it turns out well! hahah!

[Steve]

What did you do with that one yard?

I bought a $30 bag of granulated pre-emergent from the Co-op. Poured it in a walkbehind seeder/spreader walked the yard for about 30 minutes until I used it all up and then told her it would be $75. I read the directions on the bag, it said to water for best results but it's supposed to rain tomorrow so I figured it would be ok till then.

[jimlewis]

Applying pre-emergent inside a lawn is odd to us up here in the Northwest. It's almost never done up here. So it's hard to understand the need for it. But I've been on lawn care forums for long enough to understand that's standard practice in some parts of the country to prevent crabgrass and such.

To me, it only makes sense to apply a pre-emergent if you know for sure you won't need to overseed the lawn at any point this year. Around here, if we want to thicken up a lawn, we have to overseed. So if a pre-emergent had been applied, that would mean any overseeding wouldn't work. But I understand some of you all have turfgrass varieties that spread by rhizomes or whatever, right? So you don't need to overseed your lawns?

Regardless, I don't find granular selective broadleaf herbicides to be very effective. If I am trying to kill weeds INSIDE a lawn, I would use a liquid selective broadleaf herbicide like 2-4d, et. al.

So my answer is to kill off the weeds using a selective liquid BL herbicide, and THEN use your pre-emergent.