To be a Slick-dick is to send a gift to your loved one that coincidentally arrives with near perfect timing. Not something that you planned, but nonetheless something that enhances the overall experience for your partner.
In this instance the appearance of being slick would be unjustified, thus you're a Slick-dick.
Stuart sending an Easter egg making kit to Susie for her April birthday made him a "dick". Sending rollerskates that arrived just as her existing plans unravelled made Stuart a "Slick-dick".
I moved to the Silicone Valley with my rubber tits to pursue a career as a porn star. After starring in over 200 creampie gangbangs, I upgraded my tits and ass from rubber to Silicone. I get even more, and higher quality, dicks in my pussy.
Thomasville slicker is the act of using oil to lubricate the asshole of your girl. Once the asshole is effectively oiled up you take her to the nearest Thomasville with baseball bat in hand. Bend her over one of the beds in the Thomasville and proceed to buttfuck the shit out of her with a baseball bat until security comes and asks you to leave.
Joe: "Hey boss, how was your weekend?"
Mitch: "It was alright, me and my girl ran a few errands at the outlets. I ended up giving her a Thomasville Slicker though, which was pretty nice."