First, you are "allowed" to use whatever discipline method will allow you to make the best parenting decisions that you can, in the moment, protect yourself, your other children, and your property! I'm guessing that, from your comment, you set out hoping to avoid time outs, but if you're thinking that they might work where your current methods haven't, I think you shouldn't worry about being "allowed." :p
What methods have you tried? Is there anything at all that works? or works sometimes? Do you have any forewarning when a situation begins to escalate towards hitting?
We have a pretty firm stance against violence towards one another in my family. The first reaction to DD hitting me might be a shocked face, a very, very serious, firm voice with lots of eye contact, explaining that it is NOT OK TO HIT EVER. Hitting hurts. But if she keeps going, there will absolutely be immediate consequences. I'm absolutely fine with a "time-in" on the couch with me, or, if necessary for me to keep calm/safe and to help DD calm down, asking her to go to her room until she is ready to stop hurting others, or leaving the room because I don't want to be hit or kicked.
All kids respond to different things. But the things that work best for my DD (who will be 4 in September) tend to be things that I do when we're NOT in the heat of the moment to help her work through her feelings. I try to help DD label her feelings, so she can say "I'm angry" or "I'm frustrated" instead of hitting. DD doesn't have a well-developed sense of empathy, yet, but we work on that a lot. We talk about how it "feels" when someone hits DD. Imagine, together, alternatives to hitting. DD loves to role-play with dolls and animals, and sometimes there's an animal that gets very angry and behaves badly. DD LOVES to "echo" the kinds of things she hears me say, in that situation, and seems to enjoy being one the opposite side of the scenario.
Also, when I feel like we are in an escalating situation that is going to lead to a blow-up, I try to run through my options that might keep us from getting to the place where DD is in meltdown mode. Quick redirection to another activity. Try complete silliness or play to offset escalation of upset feelings. Offer reconneciton--even just a few minutes of personal attention can often head DD off. Quickly make sure that I know if she is hungry or tired (usually one of those is the real culprit).
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