You can get waxoil in a big tub with a sprayer, but I found that to be more of a hindrance than anything, followed all the instructions and stood in a tub of hot water to soften up but it still went everywhere and I mean everywhere,   The end result was gloops of stuff where I didn't want it, the manifold and exhaust was fun, pulling up to the lights with clouds of smoke pouring off the car.  The following time I decided to use the stuff you apply with a brush, takes loads longer but you get alot better coverage,  You'll need to wire brush the underside to remove any loose crud/ rust then just 'paint' anything that's not exhaust drivetrain related,  For any box sections or places you need to apply I bought a waxoil rattle can, Its a messy job and very laborious but worth it of you have a spare day,   Failing that you could take it somewhere for a professional job@mfnick had his done that way pm him for a cost   I've a couple of before and after pics somewhere I'll dig out, from when I did mine   Sent from my SM-G960F using Tapatalk