What artist used the initials ojs?

everything

Wayne Thiebaud.

Monet and Manet both used water colours.

Until the early 15th century most artists did. Also later there have been many artists who prefer the qualities of tempera to oil paint.

I am an artist myself, and know how. for drawing a picture, and wanting to make it bigger,-through art of course- you need to graph, witch takes math work to get it right.