As much as I hate to say this, a lot of the beginning is spent in trial and error. Why it
doesn't work the same for everybody is part of the mystery of marbling.
A few years ago I had trouble with some paints and wrote to this group asking for advice.
I got some great suggestions but most of them were to not use the paints I was using
because no one else had experience with them and they thought they were the largest
problem. I loved these paints so I experimented until I found a solution.
The point is, you can try changing to what other people do, but in the long run it needs to
work for you. If you like the paints, spend some time trying to figure them out. If the
paints won't spread no matter what (I don't use distilled water either), you can try a drop
of Syntrapol in the solution. Or you can try and thin your methylcel. Or you can make
interesting patterns with the paint as it is (you said some spread and had funny edges).
If your first couple of attempts are working and then your vat seems to go all funny, I
would like to suggest that you are not skimming all of the paint of the surface in between
attempts. That can mess up the vat. Also, using items that have been contaminated -
combs washed with soap, tools that got splashed with an alum solution, etc. can mess up
your vat. I had trouble in that area at first as well.
Perseverence and remember, it is fun!