The templates I told you start off with
<tbody>
<tr>
<td>
On a default theme typically the <td>'s have the class="" inside them, usually alternating between alt1 and alt2. You'll need to remove all of these and place on class alt1 on the <tr>. This is because the <td>'s would show their style over the <tr> and you cant change the style of all the <td>'s as easily as you can change the style of the <tr>.
CSS is located in Styles & Templates > All Style Options
And yeah, this is the easiest way