Using the freewheel removal tool, I’ve been able to do this solo by rolling the wheel into a wall. Obviously, I have the wheel turned in such a way such that when I am applying pressure on the freewheel with the tool / wrench, it causes the wheel to move towards the wall, not away from it. The wall “holds” the wheel for me.
This evening I realized that it is a lot harder to remove the freewheel from an 18" wheel than it is from a 16" wheel. I think I need to pay a visit to my LBS.
The freewheel is a wearing part, just like cassettes, chains, brake pads and tyres.
You have to replace or refurbish the freewheel sooner or later.
The more you ride on dirty roads and during bad weather the sooner, logically.
You can expect a lifespan of ~ 2000 km up to ~10000 km or even more, depending strongly on the conditions during use.
Some users tried succesfully to dismantle the freewheel, relubed it and assembled it again.
Personally, I think that is not worth the effort and the hassle with reassembling the bunch of tiny bearing balls.
I removed it to clean and grease because it was getting noisy after about 8 years. I could not improve the wearing noise, so changed with new bearings ( dia 3mm). It works like new now.