If you don’t need a totally smooth shave but you want it closer than an electric razor you can reduce irritation a lot by going in the same direction as hair growth instead of against. This won’t be as close of a shave as going against the growth, but it will prevent itching and ingrown hairs for the most part.

For days where you want ultra smooth I agree with someone else’s comment that it helps to use salicylic acid on the area first (I use the T-sal shampoo for this), use moisturizer after, and pick cotton underwear that isn’t too tight around the legs.

Edit for legs: Try sitting down and resting your leg on something (like the side of the tub) so that your leg is completely relaxed while you’re shaving it. I find relaxing it first (vs. shaving standing in the shower and similar where your leg is tensed) helps reduce razor irritation significantly.