IME, no need to get a specific kit to clean the keg and liquid side. I simply give the kicked keg a good rinse, then put 1-2 gallons of hot PBW solution in it. Shake the F out of it, then let it settle for a bit. Once it's ready, I run some through my liquid line (that the keg vacated) to clean. I then empty the keg out, rinse it out, put about a gallon of clear water in it and run a quart or two through the liquid side/line. Dump and pour 2-4 quarts of Star San into the keg. Swirl/shake to completely cover the keg insides, let sit for a few minutes, then run 1-2 quarts through the liquid side. Done without any additional hardware/kits.
I stopped using the picnic taps early on. I didn't like how they were prone to drip and were easy to open up if you were not extremely careful when setting them down. Went over to actual faucets (Perlick 525ss and 575ss) and haven't looked back. I'd consider using a picnic tap IF I'm taking a small keg (1 gallon) someplace.