Sourdough Starter from Scratch

I'm in San Francisco and tried making the wild yeast starter from scratch from organic flour thing, and it just wouldn't rise. So I decided to try to make sourdough starter from scratch trying to capture whatever yeast are in my SF home, using red/purple eating grapes that were starting to mold on the kitchen counter. I rinsed them extremely well, removing existing must and mold, and then placed them on a paper towel on the counter for about 2-3 weeks. As they dehydrated they started to shrivel. After about 2 weeks, a layer of must (dull dust covering) started to form, along with some small amount of mold. I then placed the grapes in a 2 cup glass measuring cup, covered them with 1/2 c of diluted pineapple juice (25% juice/75% filtered water), and left for 24 hours. The idea with the small amount of juice is to deal a death blow to any mold, but allow the good bacteria to form prior to the yeast developing. After 24 hours, I then removed the grapes and added 1/4 c KA Unbleached Bread Flour to the 1/2 cup of water-juice in the cup. I didn't want to use organic whole wheat or rye flours, because I didn't want those yeasts competing with my "home" yeast. At 24 hours I added a 1/2 of flour and a 1/2 cup of water/juice blend. Within 48 hours the starter mix had doubled in size and was bubbling furiously. I know, I know. It is only bacteria. Day 3 I added 1 cup flour and 1 cup water-juice mix. Had to move the mixture to a 4 cup glass. Day 4 I stirred it down and kept a 1/2 cup starter and mixed it with 1/2 cup flour and 1/3 cup water-juice (I am now weighing everything, so it is 1-to-1-to-1 starter-flour-water/juice). At day 5 I stopped using pineapple juice and switched to 100% water. For 2 days, nothing. Maybe 6 bubbles. So much so, I got scared enough that on day 7 I added 1 Tbsp of dole canned pineapple juice to the water and flour and Ka-Boom! The blob that ate NY City appeared in full bloom, nearly tripling in size! Since then I've been feeding it twice a day, using 1 Tbsp of Dole pineapple juice in the 1-to-1 water-flour mixture (keeping 1/2 cup starter). In the past 24 hours, I've switched back to just filtered water and no pineapple juice. I'm still getting a very respectable rise. This yeast is so much stronger than the "wild yeast on the organic flour" version. I tried using it making bread and the bread rose like it had dry yeast instead. So I'm thrilled! The bread recipe I was using called for 1 Tbsp of lemon juice. I used pineapple juice instead (canned Dole). The yeast loves that pineapple juice!. Make sure you use unbleached flour and (brita or similar) filtered water to get rid of the chloramine in the water (bleach). (Yeast have a hard time surviving in water that is designed to kill them.) So get some grapes from your local grocery store, rinse them thoroughly, dry and place on the counter on a paper towel to absorb moisture, letting sit for a couple of weeks.And then give it a try. Have fun!