So anon, here is the answer to your bobble making query. I had a little exploration of the perfect bobble, but obviously it will depend on your yarn, tension and machine.
My favourite result came by following the process I have photographed. The best ones are in the top left corner, so I shall start by explaining the process of the other technique which is less fiddly.
The middle top, and right top are samples exploring the number of rows and how this affects the bobbliness! You simple push put two needles and knit your desired amount of rows over these by hand. Top middle goes: 4r, 6r, 8r as you work down the image, and working up top right it goes 10r, 12r, 16r.
Personally I think the other technique works much better. Isolate your bobble needles by moving the stitches next to it out. Knit those 2 stitches over 2r. Include the empty needle in the left side, knit the 3 needles. Join the right needle and knit all 4 stitches. I found here 2 rows before decreasing worked best. Decrease the left, knit 3, decrease the right knit 2. Knit the 2 stitches for 2 more rows before moving the stitches originally moved back onto the empty stitches.
For reference the top left image goes from the bottom. 2r over 4 stitches, then 4R then 6r. The middle shot shows the side elevation too!