How to correctly use "多" to say "more than"?
In my opinion, all the measure words, including 年，小时，and etc, work the same way. Let's take 年 for example.


多年 should be used only after numbers x10, like 10, 20, 30, .... For
example, 十多年：teens; 20多年：twenties; 30多年：thirties; ... ...
90多年：nineties(90-99); Thus, you can't say 9多年，11多年，...
年多 can be used after any positive integer numbers like,
1,2,3,...,100,...; 年多 connotes a bit more than, usually less than
1 year. For example, 4年 > 3年多 > 3年.


The same thing for other measure words. Both 五十元多 and 五十多元 are correct, but mean differently. "十个小时多=from 10 to 11 (10.3 / 10.8...) or 十多个小时=from 10 to 20 hours" is correct too. But expressions like 55多小时 and 55多元 are incorrect. 

As for the specific question "How do I say "more than two beds" then?", you can use 多于, 不止 or 比...多. More: 多; than: 比 or 于, so more than: 比...多, or 多于; For example, there are more than two beds in my home: 我家的床多于两张; 我家的床比两张多; 我家的床不止两张;