Making fruit syrup less viscous while retaining flavor
To thin your syrup, add more water to your syrup; it will become thinner without reducing sweetness that much.  Then add a touch of artificial sweetener to restore any lost sweetness.

To strain your syrup, you can use multiple layers of cheesecloth, a fine chinois, or a coffee filter in the bottom of a strainer or small colander.  Use a spatula, spoon, or ladle to help press the syrup through the filter. Using heated syrup will allow it to flow more readily through the filter, while still removing particles.