I've only bathed shorthairs, so it was relatively ... easy? It's best as a two-person job, but can be done with just one if that one has confidence.
Mine are reasonably tolerant of the process and don't keep grudges, luckily, and they only get baths when needed (extreme dustiness or slack hygiene).
My method - first trim the cat's claws. Also, wear clothes of heavy fabric, jeans and the like.
Pre-fill two big pitchers with body-warm water and have a cup handy. Get the shampoo bottle out too. Put these at the end of the tub or floor next to the tub, somewhere within reach and easy to maneuver with only one hand.
Line the bathroom floor with towels and have one or two more to spare.
Get the cat and be sure to carry in such a way that when the cat figures out what's about to happen, she is not able to get traction off of you during the escape attempt.
As others mentioned, the smooth transition of cat into bathroom, door closed behind, and deposited into tub in one motion is key.
Side-saddle the tub edge if you can (or sit astride for better balance, but you're risking your calf and foot this way), keeping one hand on the cat's shoulder area, use the other hand to dip the cup and pour the water over the cat.
Note: At no point do I allow my cats any additional traction! If they stay still, they won't slip. If they start freaking out, without traction I can keep them contained while they skitter. Same reason I use the regular tub instead of a smaller one, they can't hook a paw over the edge.
Anyway, a little less than one pitcher should suffice for wetting the cat down. Now dribble shampoo and massage into cat (this part is usually okay, particularly if your cat likes attention!). Use the remaining water to try to get as much lather off as possible. Since you're probably racing the clock here, dispense with the cup and just try not to dump all the water on the cat at once.
Let the cat jump out (freedom!) but since the door is shut, she can't go anywhere and has to put up with at least some toweling off, just enough to stop her dripping everywhere.