I use a perfume bottle as the probe for abdominal exam. It's bottom is flat and glassy, narrow and oblong, that's why it slips good and is applicable for tilting(the best would be to find someone suchlike, but not level, but some rounded, exactly as the convex probe). For breast and neck exams I use the side of the same bottle, as a linear probe - it's less long.
As for the gel - the aftershave gel is good, also can explore any lubricant. But the best is true ultrasound gel - it's also the best as the sex lubrican't, it's very good and cheap.