RNG, LOL if I did a drawing, no one could read it.
As Eric suggested, and assuming the foot switch is nothing more than a variable resistor, wire it in series with the brake coils. It's acting to limit current flow, so put an ohm meter across the leads coming out of it and make sure that resistance drops as the pedal is depressed. Ideally resistance would be infinite with the pedal all the way up. Also make sure it's rated for the current being drawn. If the foot pedal is rated in Watts, that 6 amps will put out almost 90 W @ 12.5 volts. That's a LOT of heat.
Please don't use ScotchLocs! They physically damage the wires, which later fatigue and break inside the Loc, so they're not making contact but look like they are. For a while I switched to PosiLocks and PosiTaps, but really the best way is to strip back 3/8" of wire, tin it with a soldering iron and rosin core solder, then use a single strand of copper from a multi strand wire to wrap the two conductors together tightly. Then solder them together, and finish up with a coat or three of liquid insulation for a waterproof joint. Or better yet, route all wires to end at terminal blocks and use the correct crimp on eyelets.
Don't be one of those guys who's work I've had to rip out and replace. Draw it out on a piece of paper so that when you come back to it in six months or a year you can figure out what you did. Not to mention the poor SOB you sell the thing to when you're done with it. I don't mean to sound harsh (well, yes I do) but the absolute CRAP work I've seen on the trailers, trucks, cars, and motorcycles I've had to deal with is just this side of criminal. Spend the money to get the correct color coded wire, terminals, and crimp tools, plan and document your work, and you'll never have to do it again. Try winging it and taking short cuts, and you'll be back here crying in your beer over some weird behavior nobody can help you with because the only solution is to rip it out and do it right.
