Hey, so I've seen a few people with the marijuana leaf emblem and I'm trying to get that. Supposedly, you have to set off a chain reaction of explosives that kills an enemy to get that... This has proved harder than expected. I've been trying for quite some time now and I'm having a lot of trouble. From anyone that has it (or anyone really), what are your tips/techniques to set off the chain explosion? What are you using to set if off? Etc.

Thanks ahead for any advice. I'll choose best answer depending on who helps me achieve it :)