Make sure that your hands are warm. You can't work with cold hands. Stretch your fingers before practising. Start the cuts (that you wish to accomplish) slow. Slowness will add smoothness. Smoothness will add speed.
Skater Cut....I love it. To spin the packet, you need to kind of experiment. Just bring the packet overand and hit the corner with your right third finger (I assume that you are holding the deck in the left hand). Again, it just takes practise. I wish you all luck.
Well, it really depends on what you want. Personally, I think practising flourishes is a great way to kill time and to take a break from card magic. Try not to incorporate cardistry into your card magic routine. It's good to know some in order to attract the attention.
Sponge balls are a great props to add on part of your routine. I always use sponge balls as an opener. I have a tip for everyone who are starting the sponge balls. (I hope it is not an exposure). But, when making the vanish or the retention vanish, try to do it slowly for the audience to see...
To answer your question, if you have a soft, cloth table, it will be very easy to pull the black aces. Try using a pinky break under the selection, and as a result, it will be easy to grab. Moderators, please delete if it contains exposure.