I would use rail joiners. I would solder the connections between individual pieces of E-Z track. I would use rail joiners between E-Z track and the flex track and between individual pieces of flex. I would not solder the flex track joints except where the joint comes in the middle of a curve. When you connect the track, use a business card slipped between the 2 rails that are being joined to allow room for the rail to expand if the temperature changes significantly between seasons. For block gaps, I would cut the rail with a Dremel and cut off wheel after the track is secured, where you want to locate blocks. For insulators, save the little plastic clips that come on a loaf of bread to tie the bag closed. Cut the bread clip in strips about the width of the top of the rail. Slip the strip of "bread clip" into the slot you cut in the rail and secure it with some acc on either side of the clip material. Once the acc has set up, take a sprue cutter or flush cutting nippers and cut the plastic flush with the top of the rail. Use a small file or an Exacto knife with a #11 blade to cut away the plastic to match the webbing in the rail. When you are done, you will have an almost invisible insulator in your rail.
