A few tip's
#1 Get a Fiberglass cleaning pen its (in the video) helps prep and clean the surface of the led strip so the solder makes a good solid connection.
#2 Get a Solder Iron with a Very Small (sharp) tip. This helps you NOT over solder the connection and it keeps the heat right where the tip is. If you use a traditional gun the tip is to wide for a 11mm RGB strip and its easy to De-Solder the connection Next to the one your doing.and you could dammage the RGB stip with to much heat from a fat tip.
I use a Weller solder station, It was $120 and its a Great Investment. I also have a Hakko Station they are also great, Again under $150 and well worth it. If you have the right solder gun it makes the job much easyer and the finish product will be better.