Messy Oil Changes

First, there are twin small drains at the base of the filter housing, alan key operated, second, if not spin ons, get the adapters from DD, not expensive, makes life much cleaner.

After cracking the seal I always take off filters inside a garbage bag.

Me too, those big, thick Hefty ones. No leaks or mess.

If on DD" you drain the filters first, no need for that garbage bag nonsense, that's why the drains are there.

Yeah, I have been using large Zip-Lock bags: Break the seal, then put the bags on from the bottom up, then keep twisting the filters off inside the bag:
Leave oil-soaking rags underneath and the mess should be minimal..

Tools for everything

I use one of these
OIL FILTER DRAIN TOOL - AA473 - Tempest Oil Filter Tools - - Oil Filter Tools - Tools - AERO
The clamp on and puncture the filter then drain it out via a small hose.
Its only one size and needs to be heavily modified for anything other than a 3.5 inch filter.. but rivets and a big ass hose clamp seemed to make it work on bigger filters.
Saves a huge mess for hard to get at filters

Oceaneer

This, or use a portable oil change pump, to pump the oil out of the drain bucket/container as it's filling into a 5 gallon bucket.

If you have some room you can punch a hole in the bottom side of the spin on with a hammer and a screw driver and drain the filter oil into a bucket. When you loosen the filter the oil will come out easily. Let it drain and it makes the filter assembly a lot easier to handle.
This advice is approved by my dock neighbor with 6/71's in his 38 Uniflite.

I also put an oil absorbent pad in the bag, and use nitrile (?) gloves - less slippery if/when oil gets on the outside of the bag.

I hate to confess a not so correct way I have done things;
Get them hot, pump the sump. Next day; pump the sump again.
Then remove filters.

Yes, yes; it's not the way it's 'spose to be done. Breaks near every rule and quality rule there is in oil changes, BUT; in tight places, less mess, no burns or scars, it works.
If it's yours, you know it. If it's a customer, tell him. Then sell him a fix; remote filters and a oil change pump.

I use the garbage bag and small bucket method but always seem to end up with a clean up.

And I keep lots of oil diapers close.

The most difficult thing seems to pre-fill the filters from the 5 gallon buckets without spilling any oil.

The filters are rounded on the bottom so they wont stand up on their own when filling.

I am going to try one of those ketchup style pumps that fit in the top of the 5 gallon bucket to fill the filters next time.

how full should the filters be when I put them back on?

If the motor was recently run, I don't see the need to pre-fill the filters. If the filters are in a real easy location, straight up and down then I will bother pre-filling them about 85%. However, if the motor was run that day or the day before, there will be enough oil on the bearings and liners for the motor to run the 2-3 seconds it takes for the oil pump to fill the filters.

Interesting tool, thanks for the link.

Had same problem with Mann engine filters. I buy cheap aluminum cookie trays and make a drip pan that drains into bucket