I went through this myself and even after reading a few articles that lump sum investing was better in the long run, it was hard.
So, I decided on a two pronged approach of Dollar cost averaging: DCA1 (small regular amounts) and DCA2 (large, infrequent amounts)
DCA1: Small periodic investments I spread my mutual investments into two parts for each mutual fund, and spread the investment across many non-overlapping days in the month. Since Vanguard does not charge me a fee to invest into mutual funds, I felt that this spread captured the market ups and downs better. For example,
VCADX 9th and 28th
VTMFX 6th and 27th
etc
DCA2: Large investments....to simulate lump sum investingI saw one more pattern in the market. Market dips in the downward directions were followed by upswings the next couple of days. For example, if DOW dropped 300 points on one day, it is rare to have a similar drop on the next day as well i.e. consecutive market dips were rare. On the days the DOW (or S&P) dipped badly, there were opportunities to invest in my chosen high quality mutual funds at a lower price. When ever the DOW dropped enough (52 week lows, 300 points or more, etc), I pushed my money into one/many of my investments....if I had access to "lump sum" amounts of money, I would buy in big increments on the down days. For example, I use my tax refunds in this way. While I wait for down days, my money is waiting in a Money Market Fund OR a high interest online banking account.
More details here....
https://humblefi.com/2015/12/22/dollar-cost-averaging-my-way/This method has helped the psychology side for me while getting the benefits of lump sum investment. Hope that helps.