I don't do it!
Mostly because I get confused easily. If I'm playing two stakes and see a standard bet at that stake I sometime think its too small of a bet, or I raise my "standard" amount and its like 8BB at that table instead of 4.
Like I said I get confused easily, so for me I just play one stake at a time, there are enough tables out there that are playing on that its no big deal.
If I'm moving up and I don't want to play a lot at the new level I play fewer tables, which is probably not a bad idea anyway since I'm not familiar with that level yet and it will encourage me to pay attention and feel out the new stake with less of my bankroll in jeopardy.
But if you have a stronger mind than I do, you can probably handle it no problem- I also get distracted sometime by reflections, shiny objects, silly sounds, and sparkly things.
If you are just now moving up to the new limit. I would say cut down the number of tables that you are playing at and focus all of your attention on the new limit. Once you know that you are comfortable at this limit start adding more tables back in.
I personally play different limits and the reason for this is that i am always on the hunt for the most juicy games. What i learned is never move up in limit to where ur br cant handle it. Say if ur play 5/10 but u have a good table at 5/10 and find 3 tables at 2/5 why not play in the games where u will have the best edge regardless if u move down in stakes. Just my 2 cents.
You raise 8x BB at 2NL?
yes, sometimes even more, playing at a loose table with 40% players/flop raising 3xBB wont do any good, 6c is almost the same as 2c for players who don't know what they are doing. so i raise 8xBB, sometimes 10 or 11 with AA, has been working great for the past 200k hands!