First off, welcome to the forum and congratulations on your barely broken in 5er. If your trailer was winterized properly and bypassed the water heater, make sure you don't take the water heater out of bypass until all of the pink stuff is cleaned out - that is the last step.
Start with a pail or jug and drain the pink stuff from your low point drains - open the taps in the bathroom and kitchen before opening the drains. Drain as much as you can out of the system this way first - collected antifreeze can be used again if it is clean and you have a jug to store it in. 2nd, if antifreeze was deposited into your fresh water tank, drain it as well (hopefully this wasn't done and the tank was just drained). Once you have confirmed fresh water tank is empty, fill it about 1/4 to 1/3 full with fresh water. If it had pink stuff in it you will want to fill about 10 gallons and dump it to rinse the tank - may need to do twice. This is going to create some water so hopefully you have a place to catch it or dump it that isn't going to just run down your driveway (this is only if antifreeze was in the fresh water tank and we are hoping this didn't happen).
Moving on, make sure low point drains are closed and once the fresh water tank has enough water in it, turn on the water pump in your trailer. Now turn on the taps again (if shut off from first step) and let the fresh water from the tank run through all of your lines and the pump until it runs clear - can't put too much water through at this point in order to flush the lines. flush the toilet as well. All this antifreeze and water will just run into your grey and black tanks and you can dump it at the campground.
Another thing before taking the hot water heater out of bypass after doing all the above, I will hook up the hose to the water inlet and also run water through this in case any pink stuff ended up in that line after turning off the water pump. Afte this, then go back and open your low point drains again - there may still be some pink stuff in the lines at the end by the drains as these are low point terminations and draining them again will get the last of it out. Can also open these while water is hooked up to the trailer if you don't mind getting sprayed from some pressure.
If you are convinced that you have all the pink stuff out of your lines, check that your hot water heater has the drain plug firmly installed and take it out of bypass (usually two valves to turn on the water coming into tank - I'll try to grab a diagram off here for you). Now turn on the pump again and fill the hot water tank. Be sure to burp it with the pressure release once it fills (air pockets) or turn on the hot water tap in the bathroom or kitchen and burp the air out that way. You want to confirm the hot water tank is completely full of water so you don't burn out your electric element the first time you turn it on.
Run all your taps again (hot and cold) to remove air and same with toilet.
It sounds like a lot but it doesn't take that long and once you get used to doing it yourself it will become very straightforward. Before my heated storage when we use to winterize, I always liked to get the antifreeze well cleaned out of the system before using the trailer.
If you have an inline filtration system (most do not nowadays) make sure the filter is out before any of the above is done. Also remember to dump the filter casing of antifreeze at least twice in the process above as it is a collection point for this stuff. Lastly, dump the filter casing again at the end and then you can install your filter. I find most trailers now you are required to add in your water filter on the outside of the trailer so this shouldn't be an issue.
Now that I've over explained everything and probably covered most of what you already know - go out and dewinterize and enjoy your trip this weekend!!
