To be honest, this isn't impresive weapon. And don't be fooled, you can't actually set it off, but you wield it like any other weapon. Only thing speaking for it is that all parts needed can be bought in shop.
Like said, everything can be bought in shops. But since quality of Flamethrower Ammunition matters (and can be obtained only as ql 1), you need get ql 3 (or lower) Simple Active Tube. And depending on type of bomb you're building, 1 or 2 sets of Flamethrower Ammunition (only full stack of 100 works!). With such low qualities, you don't have to bother about ql of Key Detonator or skills involved.