welcome to that early exciting learning curve of flying
I might even go and buy another winder for now so I can just put one set on each winder.
Winders: don't worry, do what is good for you. What you are comfortable with.
Buy another winder it can help.
Or another way we've started to do is using just one winder but the left n right lines are wound/unwound separately.
Winding on one winder:
Park your kite upside down;
Leave one handle over a ground stake in correct position (eg left);
Start with the other handle (eg right). Gather the lines near that handle, squeeze together the lines and start to wrap one lineset around your winder whilst holding the handle under your arm to keep it out of the way. Sounds awkward but is do-able.
Wind this set until you get to your kite.
Untie your line.
wrap neatly on the winder.
untie the other line from your kite.
Attach this 2nd line to the same winder on top of the first line, and continue to wind in the same way until you reach the handle at the ground stake.
You should have one huge 'ball' of lines wound on one winder.
We leave the handles on to save time.
Stake in ground, hook over one handle (I usually start with red on the left);
Unwind one lineset from the handle first, get to the end near the kite, leave the line on the ground.
Turn around 180 degrees.
Put 2nd stake in ground to the side of the loose first lineset;
hook the non-handle end of the 2nd line over the ground stake and walk back towards your starting point;
where you can hook your 2nd handle over the first ground stake or use a 3rd ground stake for easy (best for novice).
I like to untwist my lines as I am walking/unwinding both ways.
So you end up with next to no twists when you start.
This is achievd by using your free hand to keep the lines apart between your fingers as you walk and unwind down the line.
Untwirl any twists when you reach the end before attaching to the kite.
Then walk your kite down the other end and attach as normal, leaving it flipped upside down.
This method only works if you have both line sets coloured differently.
left = red
right = black