Practice makes perfect. In the case of smuggling goods in and out of stations and outposts, you can definitely practice as if you actually had illegal goods while just doing legal runs. When you feel confident in your abilities, then start actually doing your smuggler's runs.
What I suggest is picking up a Diamondback Scout and fitting it with a good power plant (A rating). If you only have cash for the ship, then that's fine as well (the ship itself is already very good at low heat signature). Failing even that, I'd hope you aren't using a Viper or Eagle (mostly due to abysmal use for trade of basically any sort, but it's possible). I've personally smuggled with a Python using the stock E rated power plant, so with enough skill (and maybe some luck), just about every ship is capable of evading scans.
Try to get yourself at least moderately lined up with the letterbox (if a full station) outside of the 7.5km range (you can be risky and brazenly fly next to the station the whole time, but that really is risking a scan that has time to complete). Once you've got that setup, engage silent running and start heading to the opening (don't boost unless you're extremely confident in your ability to do so, and also not get your heat above ~90% before you've even gotten to the letterbox). The DBS shouldn't even really be getting to 50% with a good power plant during this.
Should a ship be in the way, you should have practiced enough legal entrances to know how to get around them quickly. If not: generally at least one side of the box shouldn't have a ship passing through, so go through there, but maybe slow down a bit so you can get a bit better control over your maneuvering through the box. Once you're past the box, you should be safe to disengage silent running. Dock as normal.
If you're heading to an outpost, basically do nothing different than the usual legal landing. Security is non-existent here (except for a few rare outposts, like military ones). If you got scanned here, it was either a player, or the most random of random NPCs. If you're worried, learn to speed dock at outposts. You should probably learn this anyways.