Painting step 2....Stomach Cramps

After I finished the sketching, I began to get the paint and implements of the job out. Had three different shades of red to choose. and I chose Napthol Red Medium acrylic, along with titanium white and black. The red and black I mixed to get a really cool black/purple color for the shading. Normally I paint the dark sections first, then go lighter. The good thing about Oils v/s Acrylics is that acrylics dry faster. The bad thing: lol the acrylics dry faster. I had to be very careful doing the shading not to over shade..If I screwed up I cant just scrape it off like oils. But acrylics are really opaque, so I can cover one color with another with no bleed through. As I was doing this I was assaulted with all of these thoughts of "This sucks". Thus the cramps. Now the bigger decisions occur: how much redder do I want this to be. Do I just take the mixed dark I have and ad white and make the lighter sections purplish, or, do I take a base red and make them redder?..