I do hold 4 individual bonds, but I boght them to hold for the interest income they produce, and I have no intention of ever selling them, due to the limitations you've mentioned. Instead, I'll simply receive back my initial investment when they mature in several years.
Other than exchange traded bonds with their own trading symbol, there is no bond market for the individual investor. When you buy or sell a non-muni, non-government bond, you are buying from or selling into a brokerage's bond inventory. Due to the mark-up expected by the brokerage (plus trading costs) and the illiquidity of the bond, you should expect the transaction costs to represent a sizable % of the trade value relative to a similar stock trade. Depending on the dollar amount and the bond, I've seen this calculated as low as 2-3% up to 8-10% of the value of the trade. Another way to think of individual bond trading is like a used car auto lot. Yes, you can sell your car to the car lot owner or you can buy your used car from him, but in either case you'll be paying a considerable discount or premium to the car's fair market value, as this is how the lot owner makes money.
Preferreds are a bit different, as these do have a market, although usually a thinly traded one. But preferreds have a couple of problems bonds do not. The issuer can elect to suspend payments without declaring bankrupcy, the preferred shares may be treated horribly in a hostile takeover of the company and, other than default risk, probably the biggest risk to preferred shareholders is that the preferred may become perpetual and never be redeemed by the issuer if interest rates don't drop below the issue 'coupon' rate. And I would never buy or sell a preferred stock using a market order...you've got to use limit orders, as otherwise the bid-ask spread could get to be very wide.
BruceM