For example, sell a watch for $100 and offer free shipping, get $87 and pay around $4 to ship it first class mail, end up with $83 in the bank.
Putting it on the sales forums is a mistake in my experience because everyone expects to get a screaming rock bottom deal and people will tell you they will pay and then back out and waste your time asking dozens of questions only to back out at the last minute or low ball you. Who has time for that?
Ebay is the best exposure and best way to sell but there is a price you pay for that service. Fortunately they now have a global shipping program which works really well and cuts risks to buyers and sellers.
I have 15 years experience on ebay and I will almost always sell as "buy it now" with immediate payment required (so people can't buy and pay later-- they need to pay or the sale does not go through) and I offer global shipping ONLY through the global shipping program. I have had too many international parcels get lost to worry about shipping internationally myself anymore. Yes the buyers pay more for this service but it is safest for the seller.
And yes you will get more by selling individually so I would do that unless you have a group of parts that are not worth much on their own but as a group have a sort of synergy that entices someone to buy the lot.