Typically in order to pull it off you need 2 things for your company’s 401k. You need to be able to make after-tax contributions. This is NOT the same as Roth 401K contributions. Your plan also needs to allow in-service withdrawals.
This allows you to contribute the normal 19k limit as either traditional or Roth but also contribute up to the annual total contribution max(56k in 2019) combined with employer contributions. You can then do an in service withdrawal rollover of after tax 401k contributions to your Roth IRA.
Doing so allows you to circumvent both the income limit and 6k contribution limit.