Thanks for the suggestion carlosan but, unfortunately, I had already seen that tutorial and tried it with no luck lol...
Made a 4096x4096 resolution
(which I must say looked great and I can't wait until 4096x4096 becomes considered a small resolution for video games...),
scaled it to 512x512 and it was a bit better but still pixelated.
When I make models intended for game engines like unity or such, I manage with 1024x1024 in which pixelation almost never occurs,
but as soon as I get down to 512x512, things go bad.