Here's what I did and it works pretty well. Note that you'll need access to a DS flashcart for this; you can use your own (I use an R4, currently) or borrow one.
Format emunand on SD card.
Remove SD card, format system (ONLY if you want unlinked NANDs).
Downgrade system to 4.2.0-9U using Gateway's Launcher.dat (must be done after formatting emunand, so don't skip to this step).
Use rxinstaller.nds to enable use of mset exploit.
Boot emunand in rxMode.
Profit.
You can also use any other entry method to boot rxmode, like themehax or any other hax. I just prefer mset personally.
Do note that if your sysnand is below 7.x, saves from newer games (like pokemon) won't work on systems witj sysnand above 7.x.
Wow I totally missed that the OP has a 2DS!!! Glad you pointed that out!You also can't downgrade a 2DS to 4.x, don't try to do that.
Read the thread linked above to set up CFW in your 2DS. You can't have autobooting with GW unfortunately.Since the thread exists, can I set up CFW with GW at all? My son has a 6.2 2DS and I thought it would be nice for my 7 year old if I set him up with a cold booting CFW and a bunch of installed games. I don't have CN but I do have my own GW that I been using for a year now.
It shouldn't be to difficult to show him to invoke the emunand through the profile trick. I'd recommend blocking wireless (after you've setup things) on both sysnand and emunand to avoid him accidentally updating either.Since the thread exists, can I set up CFW with GW at all? My son has a 6.2 2DS and I thought it would be nice for my 7 year old if I set him up with a cold booting CFW and a bunch of installed games. I don't have CN but I do have my own GW that I been using for a year now.