Just send the coins to the address you want them to be in, same as if you were sending to any other address. The wallet will label it as a transfer to yourself. If it's for a MN and you're adding up to 10K with a bunch of smaller inputs, you'd have to accumulate 10K+ in a single address and then transfer exactly 10K in a single transaction from there to your desired MN address.

Also, re: MN payout frequency...

The 3+ day thing is just at the start, after you've enabled your MN. After that, the payout will, on average, follow the expected rate given the current block reward and number of MNs on the network. Having run MNs for well more than a year now, I've never had a deviation from the expected payout schedule of more than a few hours either way, and the overall payout rate has always matched the expected rate.

Given the current number of MNs, staking is very nearly as attractive as running a MN. So if you don't want the hassle of managing a MN, staking may well be the better option for you. Personally, I prefer MNs because you don't need to keep the controller wallet online, which feels more secure, and you're better positioned to take advantage of the uptick in payout amount/rate that comes if/when there's a selloff or network hiccup.