Chiming in here since I went through all of that last year.

For skids, try some practice runs on wet roads or failing that, with sand covering it. Basically you are looking to lose traction so you can get the feel for it. Remember to leave extra room to stop since you are effectively reducing that ability with this exercise. The balls to the stem method wasn't working for me so I tried doing a minimal 'bunny hop' where I try to lift the rear of the bike enough for me to start the skid. This usually ends with me getting a very short skid before my weight returns and the pedals resume spinning. But it does slow me down some. A series of these skid-hops is what you are going for.

Track stands are practice, as Nagrom said. Try riding as slow as you can - it's better to keep rolling and not lose balance than to focus on balancing while not moving at all. Over time you will get slower and steadier but will likely always be working at it.

Toe clips: you can practice this while just sitting on the bike. Figure out where you want your foot on the pedal to start (on the bottom of the pedal with the clip under you) and where you need to 'tap' it to get the pedal to spin around and your toe end up inside. I find that if I pull my foot back just a little bit then the pedal is able to spin around just right. When you have that bit figured out somewhat, then you can try doing it on the move.