Regular Roundup takes two weeks for a full kill, root and all. No reason to add salt, however using salt alone will kill everything but a longer while for the salt to leach out of the soil. Roundup does not kill seeds. Roundup comes in all kinds of Glyphosate concentrate. The higher the concentrate percentage, the higher cost. Glyphosate is now available in generic formulas. Most herbicides of other brands will be glyphosate and at any level of concentrate.
Roundup Quick Pro: It's the Diquat that make it a 24 hour kill
ACTIVE INGREDIENTS:
*Glyphosate, N-(phosphonomethyl)glycine, in the form of its ammonium salt.......... 73.3% .
Diquat dibromide [6,7-dihydrodipyrido (1,2-a:2’,1’-c) pyrazinediium dibromide] ...... 2.9%
OTHER INGREDIENTS: ............................................................................................... 23.8%