You should wait before filing your DS-260 after having obtained your OPT EAD card, but no later than October 1, the beginning of the new fiscal year for the DV. I strongly recommend that you seek to adjust your status to DV green card in the US, with USCIS, rather than at a consulate abroad, because your chances will be greatly diminished abroad, especially if you happen to have a high number, for consuls abroad are unpredictable, arbitrary and often capricious. An immigration attorney representing you will have much more control of your case here in the US where you'll have the right to due process under the US constitution attach to you, than in a consulate overseas where you will have no rights whatsoever and besides a consular visa denial is not appealable, not at all so with USCIS.
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I agree with my learned colleague that such filing should be aimed at filing in the U.S. with a U.S. based counsel to better the chances of its successful processing eventually.
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