Solder paste?:thinking: Solder paste is used for reflowing LED's onto mcpcb's.
As far as useful tips go make sure you have at least a few spare chips. When I was working on one of the chips I accidentally broke off one of the legs when bending it ( I wasn't being rough either). After you bend both outer legs down you can then snip off the center leg. If your not comfortable bending the legs you can use a tiny piece of copper wire in between the legs to connect the stacked chips. I'd recommend alligator clips, a small clamp, etc. to hold the chip in place while soldering. Once you have one leg soldered you can remove the clamp as the cooled solder will hold the chip in place; assuming your solder joint is good. The first time I tried to stack some chips I had to desolder the joint with my solder sucker and redo the joint. It takes practice depending on the skill level of soldering you are at. For these chips I find it unnecessary to pre-tin the contacts on the chip. Just heat up both legs at the same time with your tip for a second and apply your solder. Also you hardly need any solder at all for the small legs, just a tiny dab is more than enough. The larger tab connection (ground) requires more solder then the tiny legs though.