So, What exactly is needed for Basking?

In order for Red ear sliders to bask, They need a UVB bulb, as well as a heat bulb.

The UVB bulb should be rated for at least 5.o%. Stay away from the Terrarium bulbs rated for 2.o UVB, They do not produce enough UVB for turtles needs. In general you want a UVB bulb rated for between 5.0-10.0%. With a 5% you would want the bulb closer to the turtles basking area, now with the 10% you would want to move it a little farther away because the rays can be to intense and hurt the turtles eyes. Making the eyes puffy and reddish.

If your RES is showing signs of red, puffy eyes, I would suggest moving the UVB basking lamp farther away from the turtle and see if that helps.

Now, lets address the heat part of it. This can and is most frequently done with a common household bulb(Incandescent). I am currently using a 60 watt, however some people use 45watt, 75 watt, 100 watt, whatever. As long as what ever bulb you use gets the basking area about 10 degrees warmer than your water temperature. This gradient in temperature is large enough that the turtles will want to bask to digest food and warm up. But not so large that your turtle will get a possible temperature shock from the huge temp drop when they enter the water.

Another thing to keep in mind would be that UVB rays cannot penetrate through glass or plexi. and screen with 1/8" or less holes will limit The UVB by 30%.

and MVB bulbs...well thats a whole nother story. Maybe some other blog, some other time.