Named styles are ever so much easier to handle. This is my style for the "first" paragraph in a chapter or section:
p.first {
margin-top:0.5em;
margin-bottom: 0.0em;
text-indent:0.0em;
text-align:justify;
}
It's evoked of course by going <p class="first">
My style sheet can be seen at notjohnkdp.blogspot.com (posted in 2013 but often updated).