Boss Rush tips?

[Phaper]

I'm at the point where just about the only runs I have left to complete are Boss Rush.

Does anyone have any tips?

I've gotten some really nice runs, but I can't seem to beat Mom by the 20 minute mark.

[Kyukyu]

Look for Item Room (& shop if you have the keys + 15 cents or more) and nothing more. Book it for the Boss Room right after. The only things I take time for when trying to go for Boss Rush are tinted rocks and getting keys/bombs if I need more of them.

[H2R]

Just quick restart (Press "R") constantly until you begin your game next to an item room. Then if the item is considered as a starter (I think you might be able to find a list of those starters on google, but basically if the item gives a significant dps increase) you pick it, otherwise you quick restart again. Once you have your starter, dont waste your time visiting every single room, if you think you have enough dps to handle boss rush, just go for the boss of the level directly no need to lose time looking for the item room if you found your boss room first. Visiting an early shop might be a good idea if you can get a mapping item you will save seconds/minutes.
Using what I just described, I almost get 100% boss rush. And I'd say that if you did not get your boss rush, you should have restart your game a long time ago ;)
Hope this help, my english is not perfect sorry.

[Regrettable Acts in 1 Step]

If azazel, get tammy's head to get full 360 brimstone, get broken mirror as it increases brimstone range by 100%

Isaac kerp rerolling non helpful/dps (even health) till u get good dps and DONT MISS 2ND FLOOR DEVIL DEAL

Maggie CANT miss an item room and 2nd floor devil deal. Getting goat hoofs and restart until item room near entrance is advisable.

Blue Babby, hope to god you'll get a 4th spirit heart by the end of 2nd floor and get an angel room (no 3 spirit heart requirement) or take the devil deal that help (leaving 1 hp)

Judas is ez because you have book o' belial, get good damage and hp then use belial on necessary room, getting 2nd floor deal with da devil is advisable, but not mandatory.

Lazarus, need to get 2nd deal with the devil then suicide for Lazorus mk.II.

The Lost, Keeper, and Eden... sadly i cant say much ( because of the randomness of all of them ).