Worried about oil remaining after sucking it out?

Just add a couple of quarts of inexpensive oil back in and crank the
engine.  The oil light will go out indicating you have good oil pressure.
Run for a few minutes to thoroughly dilute the remaining dirty oil.  Now
suck out the 2 quarts of oil, change the filter and fill with new oil.

If you really want to clean the insides, flush with a couple quarts, suck
out and replace the filter and flush with another couple of quarts, suck
out and change the filter again and fill.  The cost of 4 quarts of oil and
an extra filter is minimal for the satisfaction of having a clean engine.

I seen people add kerosine to the crankcase of marine engines and run them
to flush out the dirty oil.  This is, however, insane.