How to disable initial block download
For set up the dns seed node, the parameter can be directly specified in chainparam.cpp if you are using bitcoin source in line that reads as "

vSeeds.push_back(CDNSSeedData("someaddress.com or IP addy", "someaddress.com"));

And  you need to add all the seed node IP address to the A records where  you have your domain name from. You might need to do it on your own if you have a privater server or can use cpanel depending on the scenario at your end. I did it via cpanel as I have domains hosted with siteground.